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dp
08-03-2008, 02:24 PM
Anyone tried using a modified radial arm saw for a surface grinder? Something needs to be done to keep the dust out of the motor, but for clean up work it seems like it might be feasible, and in the realm of home shop machinery solutions. I'm curious because I just picked up an older Delta Super 900 saw in utterly excellent shape for $40.00. An example is shown here: http://www.owwm.com/photoindex/detail.aspx?id=3825

What a great site that is for older woodworking machine information!

wierdscience
08-03-2008, 03:18 PM
I have three radial arms at the moment,everything from a 10" Sears to a 16"Dewalt.I have used them for saw blade grinding,but I don't think they would do to well for surface grinding.

The saws frames even the big monsters like my Dewalt are pretty limber.I haven't checked but my gut feeling is that there is atleast .005" deflection from just the weight of the saw head moving over the arm.Since .001" is a fair pass on a surface grinder I think t would be a waste of time trying unless you made serious mods to the saw.

Something like an arm support to tie the end of the arm to the base would be a start,but even then.

Next problem would be the track bearings,they aren't that great,usually a fair amount of slack up and down too.

The one I used for kiss grinding saw teeth worked because it only needed to hit one small spot in the same location time after time.Trying to maintain any kind of accuracy over say 16" would be difficult on RAS.Over 4 or 6" might be doable to some degree of accuracy.

SGW
08-03-2008, 03:34 PM
In addition to the (relatively) lousy bearings and the deflection, I suspect there would also be far too much vibration to get any kind of decent finish.

Evan
08-03-2008, 03:53 PM
Build a swing grinder from a cheap import drill press instead. It's on my list of things to do, still...

http://vts.bc.ca/pics/swinggrinder.jpg

Alistair Hosie
08-03-2008, 04:04 PM
Evan I seem to remember asking this before,but couldnt with the correct fitting a milling machine be used as a tempoary surface grinder.I should think this would work better than a r.a.s. as it is beefier and stiffer especially with power feed???Alistair

Bill Pace
08-03-2008, 04:14 PM
I've got that same Delta saw.... (I paid $50 for mine) found at a garage sale maybe 10-12 yrs ago mounted to a most "robust" bench (read: "overkill construction") , figured the bench was worth close to that. Turns out the bench was about all I got out of it, the saw is badly underpowered. Would do trim stuff, but put a 2x6 in it and it couldnt handle it. Have you tried yours yet Dennis? Does it seem underpowered? I lean to thinking that my motor is bad, but having no more in it than I did, I have just shoved it back in a corner and try to ignore it .... I did put that bad-boy bench to good use!

FWIW ... I would have doubts that a radial saw would do much as a surface grinder, for the same reasons already mentioned, marginal bearings and flex in the arm ---- course, it'd be simple enough to give it a quick test, one of the thin wheels should mount with out any mods, cobble a magnet and try out on some scrap----

loose nut
08-03-2008, 04:36 PM
Hsm magazine did an article on this topic many years ago and the results were less than bad.

Evan, I have seen these swing grinders before but was told that they were very dangerous, grabbing the work and throwing it at you if you had to much of a cut, if this is not the case or the chance of this is rare if used properly could you do a little write up on them, it looks like a good solution to the at home "low use" grinding needs.

Paul Alciatore
08-03-2008, 04:38 PM
A few years ago I purchased a Sears radial arm saw for work. I tried to set it up, per the manual and had a lot of trouble. None of the adjustments held - and I am talking 1/16s and 1/8s inch deviations, not thousanths. I noticed I was moving it around on the floor to more easily reach the various adjustments and a quick check revieled that each one changed with even a small such movement.

I made some floor mounts and bolted it SOLIDLY to the cement floor. Made sure everything was very tight on the mounts. Then did the adjustments one more time. Everything held perfectly. First try. And it has held for at least 5 years now.

They could have saved me six hours of work if they had been up front about the lousy stand. Radial arm saws have a bad rep among carpenters and you will almost never see one in a cabinet maker's shop. This is apparently why.

I like Evan's idea better, but if you want to use a radial arm saw, I would add an X-Y table and lock the arm down for use. Extra bracing (fixed) on the arm would also be a very good idea. But I suspect you will still have problems.

Evan
08-03-2008, 06:53 PM
I don't have any experience using a swing grinder but they are common as low wages in the foundry business. They use ones that are suspended from chains, arms, booms or stands and use them to grind off flash etc. John S sent me this picture and I think with proper care and some guarding to prevent the work shifting toward the operator it would be reasonably safe. I sure don't like the idea of using a radial arm saw. I have a 10" Sears made about 30 years ago and that tool scares me almost as much as a chainsaw, maybe more.

ulav8r
08-03-2008, 06:58 PM
Just mount a vice on the table of the swing grinder. That is how punch grinders are set up.

riceone
08-03-2008, 09:28 PM
I have a magnetic vise that I use on my mill to do the little surface grinding that I have to do. riceone

J Tiers
08-03-2008, 09:44 PM
The drill press grinder idea may not be quite as bad if the words "cheap import drill press" are replaced with something more expensive.

In case someone does not know, the cheap ones often (not always) have ONE bearing down by the chuck. The other end of the skinny spindle is just trapped in a sloppy spline driver at the top of the head.

That dude will walk the stone right up on the part as the skinny spindle deflects and moves in the splines, and then sling the work somewhere when it gets in a bind. or maybe it'll just break the stone and sling the whole works.

If it won't work as a cheap mill, it sure as heck won't work as a cheapo Blanchard grinder.

I still wouldn't LIKE it, but it wouldn't be quite as much of a guaranteed problem with a more solid press.

Almost as bad as the trimmers at a vacuum-forming plant I visited..... drill presses with circular saw blades chucked up, and some minimal guarding. Couldn't guard them really well, the work had to slide in to get the top trimmed off.

Note to self, do NOT lift hand UP!

bruto
08-03-2008, 11:21 PM
I don't have any experience using a swing grinder but they are common as low wages in the foundry business. They use ones that are suspended from chains, arms, booms or stands and use them to grind off flash etc. John S sent me this picture and I think with proper care and some guarding to prevent the work shifting toward the operator it would be reasonably safe. I sure don't like the idea of using a radial arm saw. I have a 10" Sears made about 30 years ago and that tool scares me almost as much as a chainsaw, maybe more.

If your 10 inch Sears saw scares you enough that you don't want to use it anyway, check out this site:

http://www.radialarmsawrecall.com/faq.asp

I like radial arm saws myself, and regularly use one of the recalled ones, but if a better guard will help, you might as well get one, or if it's too old and is going to be consigned to scrap anyway, you might as well get something for it if you can.

Tuckerfan
08-04-2008, 05:22 AM
Anyone built one using these plans? http://www.dm.net/~lughaid/vest.htm

pcarpenter
08-04-2008, 10:54 AM
Guy Lutard has a bit about making a simple "spot grinder" using a cheap granite surface plate. You take it to a counter top shop and have them bore a hole for a vertical column and then make a work head. The work is just slid back and forth under the launcher...uh...er workhead by hand:D The key is that its used for spot grinding by grinding the highest spot first and then *very slowly* working downward until the piece is flat...maybe taking a few tenths at a time.

As for using a milling machine....I would say forget it unless you are trying to destroy it. You will end up with the equivalent of clover lapping compound on the ways as bits of silicon carbide mix with oil and get trapped between the way surfaces.

Real surface grinders have totally covered way surfaces. That is, no portion of the oily way surfaces are exposed when you run the table back and forth.

Paul

dp
08-04-2008, 11:38 AM
Coupla things: I was thinking more in terms of using a diamond wheel for final finish and not so much for metal removal - I have a shaper for that :). With the center pivot arm a work area of 6" should not create a great deal of flex in the arm but it remains to be seen. Certainly moving the head end to end would do so.

As for RAS generally, I have used them for 30 years and enjoyed the versatility and ease of setup but you need to pay attention to some details. Use the proper hook angle for the job! This saw I just bought came with three high positive hook angle blades, all of which will go into the dumpster.

Alignment is a real problem, especially if the saw is on a mobile bench. Even the over-built bench from DeWalt/Delta is not stable. I've created a three-point base using hefty angle iron to avoid the 4-point base that comes with the saw. It holds alignment much better. I also built a square alignment "blade" from 3/4 MDF. It is ideal for aligning the table vs using a real blade, and I get fewer cuts on my fingers. A toothless blade solely for the purpose of alignment would be a nice feature even for a table saw but I've never seen one.

tiptop
08-04-2008, 01:57 PM
Dennis, before I found my surface grinder I had thoughts similar to yours in building one. First off I would suggest you read page 58 through page 68 in Guy Lautard's Second Bedside Reader. This article explains a fairly simple solution. This combined with parts of you radial arm saw could give you decent end results I believe. When I started making one I used only the verticle column and adjustment mechanism from the saw. I also changed the screw inside of the column because it was 8 toi and I wanted 20 tpi. Mine had a 1 to 1 gear ratio to change the horizontal shaft to the verticle shaft. This ratio could also be played with to get finer feed. I did not use any of the Arm parts or motor from the saw. I had a motor off of a surface grinder (ebay) and built mount and swivel plates for it. You could use any motor and then you need an accurate spindle. I started with the hand feed found in Guy's book. This worked well for me. Use all the cautions recomended. I started looking into lineal bearings and build a feed table when I found the grinder I have now. If you would like to see pictures of what I had I would be happy to post or forward them to you. Good luck, it is a fun project and not insurmountable. Jay

dp
08-04-2008, 02:08 PM
Interesting idea, Jay. I have a second saw that is a simple non-pivoting arm DeWalt that would be a good candidate. The table and pillar are exceedingly strong and I can see some possibilities here. The motors on these saws have flat bottoms which for cutting wood is a good thing but may have no advantage for metal. I've been considering building a universal pillar from a used drill press I have in the corner, so this may be a way to recycle some old equipment into something more useful.

Mcgyver
08-04-2008, 02:53 PM
even on a semi decent surface grinder, you can work to a 10th and still get a crappy finish. In other words the lack of rigidity and very expensive bearings in excellent shape manifest themselves as surface irregularities which are much less than a 10th of a thou. 100th of a thou? a millionth? I don't know but the difference between a great finish and a lousy finish is a lot less than a10th.

This leads me to suspect the grinding ideas involving anything but very high quality spindles, smooth accurate motion and heavy castings (to dampen vibration) will be less than satisfactory. that's why spindles and quality grinders cost so much - ie dumore's cost thousands and dremels cost 50.

That's why i think a lot of these attempts at make a surface grinder from something else or a tool post grinder from a dremel are efforts at turning the sow's ear into the silk purse, however well intentioned. One of Lautard's books describe fixed spindle grinder with a surface plate underneath - the work, held by hand, is slid along the plate under the wheel until it sparks out. There you have a fighting chance in that all you have to worry about is the spindle, accurate linear motion is taken care of, but you won't catch me running a set up like that, a missing finger waiting to happen.

fortunately, there are techniques for those without surface grinders to get the same results; scraping for flatness, lapping for hardened stuff, filing and abrasives for finish etc so similar results can be achieved....imho effort would be better spend on building skills there while saving for a grinder. sorry to be the wet towel on it, but i have to call em as i see em

dp
08-04-2008, 03:12 PM
fortunately, there are techniques for those without surface grinders to get the same results; scraping for flatness, lapping for hardened stuff, filing and abrasives for finish etc so similar results can be achieved....imho effort would be better spend on building skills there while saving for a grinder. sorry to be the wet towel on it, but i have to call em as i see em

That's a helpful response. Life is full of common sense and some of that equates to wet blankets. That can be a good thing!

lazlo
08-04-2008, 04:05 PM
Guy Lutard has a bit about making a simple "spot grinder" using a cheap granite surface plate.

That jury-rigged surface grinder that Guy Lautard describes in the 2nd Bedside Reader is a bit frightening -- essentially a horizontal grinding spindle mounted above a granite surface plate, and you push the part through with your hands (!)

He backed way off on that description in the 3rd Bedside Reader, with all kinds of CYA safety warnings (it was safe for the retired tool & die maker, but don't try this at home :) ).

If you really need a little surface grinding, seems a lot safer, and less kludgey, to mount a stone on your milling machine. But make sure to protect your ways!

Evan
08-04-2008, 04:34 PM
I don't know but the difference between a great finish and a lousy finish is a lot less than a10th.

It's an optical difference. You can easily see the difference in a surface finish that varies by only a few wavelengths of light. Green light has a wavelength of 510 nanometers which is 0.00002".

BadDog
08-04-2008, 05:48 PM
Poor Man's Surface Grinder
I thought a poor man's surface grinder was, well, a surface grinder. :D With small SGs often selling for well under $400 including mag chuck and some wheels, why bother with rigging something of highly suspect (to near non-existent) value?

I'm so cheap I Scrooge look like a whale in Vagas. And even then, the only reason I can think of is to save space by having multi-purpose tools using what is already on hand. But something like this is modified to a dedicated machine, and for a cost in BOTH parts AND labor vastly exceeding what you could get the real thing for. Even if the base starter machine was already on hand and in good shape, and the results were guaranteed to be of sufficient quality to function adequately, I would bet this is still a loosing proposition.

With stuff like this, my "luck" (foresight, knowledge, experience, skill, brains, etc.) is so bad that I often "loose" even when firmly convinced I've got a sure thing. To me, on a project like this, looks like ALL the cards are stacked against you, so there is no way I would attempt anything of the sort.

.RC.
08-04-2008, 06:48 PM
You could always try to make one out of an old shaper..

lazlo
08-04-2008, 09:35 PM
I thought a poor man's surface grinder was, well, a surface grinder. :D With small SGs often selling for well under $400 including mag chuck and some wheels,

Yeah, keep gloating Russ -- none of those $400 surface grinders ever show up in Central Texas :)

J Tiers
08-04-2008, 10:21 PM
I think he's wrong anyway.....

BIG surface grinders, perhaps with some "issues" go for under $400.

SMALL ones, such as a Sanford, go for significantly more, since a far larger audience can use them.

Why NOT sell a large SG for cheap? The bearings for it, if even available, may cost a cool $5000, if you get ones that are capable of what the machine is (or WAS) capable of.

Then, another large expenditure of money or time on the ways, etc, etc, or there is no point in the bearings. And more $$ and effort on other things, or there is little point in the bearings and way restoration.

By the time you do all that, you are likely at several times the cost of an import SG which will work right away, and do 90% of what most anyone would want.

So, a large SG in "less than perfect" shape is worth, well, scrap price.

JCHannum
08-04-2008, 11:23 PM
FWIW, it is not at all unusual around here to see small 6X12 or 8X18 surface grinders go in the low hundreds and sometimes less. Good working machines, not clapped out junk. They will be manual, but they are cheap and plentiful.

Granted, Sanfords are hard to find, and do command premium prices for no other reason than their rarity.

BadDog
08-05-2008, 12:12 AM
I think he's wrong anyway.....

Oh really? I'm in the "tool desert" and picked up a "low use" (still visible scraping on most all way surfaces) BS 612 Deluxe with chuck (fine pole permanent mag) but minus base for $400 even. However, it was in "kit form". Good part of that is all critical pieces were easily inspected. I decided since that I paid too much really. I've seen several since then that were "running" and "in use" (though didn't inspect ways) for less, sometimes quite a bit less, though sometimes with no chuck. Finally saw one I couldn't resist (like I need 2!) for $50 with Electro Mag Chuck and base. But turned out that one has some issues with the spindle (coolant intrusion) and significant wear on the ways. I figure worth it for the chuck and base.

Now, tell me which of these I'm wrong about? Or which of these wouldn't make a better "surface grinder" (including wear, or $50 grinder needing $100 worth of bearings, not $5000) for less money than a cobbled up drill press or radial arm saw?

batt-man
08-05-2008, 07:53 AM
Has anyone tried the plans in the book "the shop wisdom of philip duclos" (i think that's spelt correctly) where he makes a surface grinder head for his milling machine?

To me it looks like it'd do a good job; obviously you'd have to rig up some kind og cover for the mills ways, but still for the occasional user it looks like a good idea.

J Tiers
08-05-2008, 08:04 AM
Now, tell me which of these I'm wrong about? Or which of these wouldn't make a better "surface grinder" (including wear, or $50 grinder needing $100 worth of bearings, not $5000) for less money than a cobbled up drill press or radial arm saw?

I figure that the larger ones go for LESS than $400, or scrap price, whichever. And smaller ones, of which the Sanford is one, for HIGHER prices, simply because more folks can use the small ones.

If your large surface grinder can use several $25 electric motor bearings and produce sub-tenth finishes, then either your motors in your home country are a lot better than ours, or else your surface reference needs calibration.........

After 30+ years of industrial use, most machines need a re-build. I am glad for you that in your home country they do not.

Better than a cobbled-up drill press? I suspect that could be achieved with some 400 grit and a block of wood, .........but I never supposed that a cobbled up drill press was worth even messing with, so I haven't the least idea why you brought THAT up with respect to what I wrote.

lazlo
08-05-2008, 09:55 AM
Now, tell me which of these I'm wrong about? Or which of these wouldn't make a better "surface grinder" (including wear, or $50 grinder needing $100 worth of bearings, not $5000) for less money than a cobbled up drill press or radial arm saw?

I think that was a bit of exaggeration on JT's side to make a point: even a matched pair of Fafnir, GMN, or Barden ABEC-9 angular contact bearings are "only" $600 retail.

Surface grinders usually use 1 or 2 matched pairs of precision radial bearings, which would run you ~ $200/set. A 6x12 or 6x18 surface grinder has probably seen a long life in an industrial shop, so whether the rest of the machine is worth that expense...

oldtiffie
08-05-2008, 10:08 AM
And don't forget or neglect wheel balancing.

Dynamic balancing of the rotor assembly after replacement bearings while perhaps not essential certainly helps.

pcarpenter
08-05-2008, 10:59 AM
I got my Rockwell-Delta free....well...it took a little nerve to ask the school superintendent if I could rescue it from an untimely death. It also took lots of sweat as my wife (I really love her) and I figured how to get a top heavy item with no lifting points up onto my utility trailer with nothing but a shop crane as drivers-by watched what appeared to be some guy and his wife stealing stuff from a local high school at dusk :D

Seriously, however, I did watch ebay for a while before I was blessed with this opportunity and this same grinder and many others in its size class often do go in the low hundreds of dollars. If a guy scored one for say three hundred dollars and then spent a couple hundred in gas driving to somewhere where machine tools are not made of unobtanium, you could still have a surface grinder for say $500.

Bearings....well some may use a bunch of pairs but its my experience that the smaller ones do not. My Delta is the newer design with a single angular contact ball bearing front and rear. The older design uses a plain (plane) bearing in the front and you can be sure that's no longer available. While lots of bearings may help make for a precision spindle, the load factor that might be the reason for lots of bearings in a mill spindle is a non-issue in a small surface grinder.

The thing that I think one should really watch out for is that some grinders use circulated oil to the spindle bearings. Pumps die and people figure that our when the bearings are subsequently ruined. The bearings in my grinder and some others are oil lubed with a cup...meaning that reliability of the user is critical, but at least there is no pump to fail.

While spindle bearings are critical, you can be sure that unless completely galled up and ratchety, even a surface grinder with some wear on it will likely perform better than the radial arm flesh ripping system originally proposed.

Its important to note that Lutard made clear that the grinder he described is for spot grinding and as such should never be removing enough material to really grab the work. In spot grinding, the machine should never have the opportunity to make a "full pass" across the work with the wheel cutting. Its a process that more closely approximates scraping. I too am afraid that absent this understanding it could become really dangerous.

The up side to this spot grinder idea is that the architecture of the design is not so critical. There are no precision sliding way surfaces to create and the wheel only touches the work in exactly one spot directly under an un-movable cutter head so that perfect planar relationships are not so critical. With a radial arm saw adaptation, the lack of precision of the arm with relation to the table is likely to produce a machine that makes tapered parts...likely of higher tolerance than the original as-milled part.

Paul

JCHannum
08-05-2008, 11:17 AM
The Rockwell Delta Toolmaker is probably one of the best values for the HSM. They are small enough for the home shop, and have the advantage of being a T&C grinder as well. They also frequently go for very low prices, I have bought several for under $100.00. For some reason, they do not command the price of the Sanford, but are a much better and more useful machine IMO.

The later model with the steel base uses plastic strips on the table ways, and these should be inspected before purchase as they are sometimes badly worn or missing. I don't know if there is a suitable replacement available.

Older, small, KO Lee T&C grinders can often also be had for very little money and are very useful as a small surface grinder as well as a T&C grinder. I bought mine for $5.00 fully tooled.

pcarpenter
08-05-2008, 11:50 AM
JC-- regarding the newer Rockwell-Delta and the way surfaces. You raise a good point. I will offer a different view. Mine had the pieces of teflon "tape" loose. I found a precision thickness self-adhesive tape made by the Rulon folks that should work well for this at a very reasonable price from McMaster-Carr. I have not yet ordered it and fixed mine up, but it looks very simple. One can argue that this design makes for little or no wear on the mating face on the bottom of the table and means that the average guy can get one of these back up and running for little or no money.

I was fortunate in that I got the whole toolmaker "option" which offers a pair of centers and a swiveling table, the Unihead (indexer) and the univise-- a device most practically suited to grinding single-point tools or maybe drill sharpening as McGyver has shown with his shop-made equivalent. Someone considering one of these may not get all the goodies as they seem to more often than not be without them. However, the Univise and equivalents are available as knock-offs, and the unihead is easily replaced with another indexing head. Only the swiveling table for grinding longer tapers is somewhat unique.

I would second your notion that these grinders....while not on par with a good Harig, or B&S are perhaps ideally suited to the home shop since they go cheap and are really universal....not to mention their convenient form factor (small footprint).

Paul

JCHannum
08-05-2008, 12:15 PM
Paul;
I will be interested in seeing your experience with the Rulon on the Rockwell machine, it could well offer a simple repair for these machines. Please keep us posted.

lazlo
08-05-2008, 12:23 PM
The Rockwell Delta Toolmaker is probably one of the best values for the HSM. They are small enough for the home shop, and have the advantage of being a T&C grinder as well.

Don't the Delta Toolmaker's have some kind of tapered plain bearings? I'm pretty confident replacing ball-bearings in a spindle, but how difficult is it to replace/repair/re-scrape plain bearings on a little surface grinder?

pcarpenter
08-05-2008, 12:25 PM
The old model has a tapered plain bearing at the front. The good news is that they supposedly last a long time if they don't get grit embedded.

The newer design uses angular contact bearings.

Paul

BadDog
08-05-2008, 02:55 PM
I figure that the larger ones go for LESS than $400, or scrap price, whichever. And smaller ones, of which the Sanford is one, for HIGHER prices, simply because more folks can use the small ones.

Haven't seen the first Sanford out here. But I was looking for (wanting) a Rockwell "T&C" and unable to find one for a decent price. I did miss one for $50 on Craigs List (along with a small Atlas shaper for the same price! Argh!). So I'll give you that. The (roughly) 5x10 micro(?) SGs are hard to find. But my "larger" (with $5000 bearings!! whatever :rolleyes: ) 6x12 does often go for "scrap price". From what I've seen, the 6x12s are among the most common AND cheapest for both purchase and repair. I can get BS OEM spec bearings for right at $100, I didn't make that up. In fact, they are waiting for me to get back to my grinder projects... Why you seem to think there is such a huge difference between Sanford/Rockwell and BS/etc. 6x12 (or even 6x18) is beyond me...


If your large surface grinder can use several $25 electric motor bearings and produce sub-tenth finishes, then either your motors in your home country are a lot better than ours, or else your surface reference needs calibration.........

I never said anything like that. Where you got "large" or "electric motor bearings" (much less $25) is beyond me. Funny how just a few lines later you start playing language lawyer after pulling this stunt, but that is very much in character.

Not only that, but where do you get off with cracks like "your home country"? Sad really...


After 30+ years of industrial use, most machines need a re-build. I am glad for you that in your home country they do not.

Ooh, impressive, another crack about "home country". You're on a roll! :rolleyes: But I'll give you that 30+ years of grinding likely needs a rebuild. But then many 6x12s seem to have just sat in the back for the "odd job". Oh, and before you start, I'm not making that up either, I own one that cost me $400 exactly...


Better than a cobbled-up drill press? I suspect that could be achieved with some 400 grit and a block of wood, .........but I never supposed that a cobbled up drill press was worth even messing with, so I haven't the least idea why you brought THAT up with respect to what I wrote.

And now we have the classic "language lawyer" that doesn't even make sense. Quite ironic given your earlier attempts at "putting words in my mouth". Let me clarify. My post was on topic and addressing the discussion on various "poor man's surface grinders", including cobbled drill press and radial arm saws. I suggested that in my experience the actual commercial SG applied as such a thing. You replied with a bold "I think he's wrong anyway.....", followed by what in my experience is an equally bold exaggeration of costs to own a "large" SG (wow, I'm feeling all "professional" now that I found out I own not 1, but 2 "large" 6x12 SGs!!!). On the off chance that you had "assumed" I had (and was talking about) some massive beast of a grinder, I clarified with actual experience AND referenced it back to the original topic (damn me for trying to keep on topic on this board!) of using converted drill press grinders and such, which WAS my only point in joining the discussion to start with. I never said every word I typed was specifically addressed just to you and targeted at one single post of yours. YOU jumped to that conclusion (among several others it seems).

And yet again I am reminded why I started spending free time anywhere rather than wasting time posting here. It's not worth it with the drama and frequent OT wanderings injected by some members. I keep getting sucked into this garbage because not responding is implicitly taken to "agree" or be "proven wrong". I think I'll go back to silent mode and visit HSM as "port of last call" only when bored with nothing else to do. Fortunately most of the members that I respect (though sadly not all) also participate on the other boards where the trouble makers generally do not.

BadDog
08-05-2008, 03:04 PM
I think that was a bit of exaggeration on JT's side to make a point: even a matched pair of Fafnir, GMN, or Barden ABEC-9 angular contact bearings are "only" $600 retail.

Surface grinders usually use 1 or 2 matched pairs of precision radial bearings, which would run you ~ $200/set. A 6x12 or 6x18 surface grinder has probably seen a long life in an industrial shop, so whether the rest of the machine is worth that expense...
The BS uses a single matched set at the front of the spindle with a single at the rear. And I have been offered a set (don't recall the spec or brand and they are not here) new in the box for right at $100. However, these are "surplus" rather than retail. And I don't recall them being a "high end" brand. However, I'm not talking about building a high end machine on the cheap. I'm talking about spending well less than $500 for something that will easily eclipse the machines discussed on this thread, even if sub-optimal off-brand ABEC-7 bearings were used. In fact, I would not be too reluctant to suggest that my $50 scrap price worn out BS 6x12 (that came with an electro chuck) and "$25 electric motor bearings" would eclipse anything else suggested in this thread. <shrug> That's all I'm trying to say...

macona
08-05-2008, 07:55 PM
Theres one of the little Sanfords on CL right now local to me:

http://portland.craigslist.org/mlt/tls/781226888.html

Like I mentioned in another post I just changed the bearings in my machine. I bought it knowing that the bearings were going to have to be replaced. Even then I paid $1200 for it with a 2HP vfd because the ways were straight.

A matched set of 15 degree AC ABEC 7 GMN bearings is $205 from my local spindle shop. (C&M Spindle)

dp
08-05-2008, 08:06 PM
The Rockwell Delta Toolmaker is probably one of the best values for the HSM. They are small enough for the home shop, and have the advantage of being a T&C grinder as well. They also frequently go for very low prices, I have bought several for under $100.00.

If you see another in the PNW, let me know!

LEOTECHCNC
08-05-2008, 08:06 PM
I would think that an old shop smith would give a better foundation for a limited capacity surface grinder. Harbor freight has a good picture on their website of a 10 in 1 woodworking machine. You would need to build a rack and pinion powered sliding table. But I think you could get away with chucking a aluminum oxide wheel on the spindle.

oldtiffie
08-05-2008, 09:46 PM
I agree with the general thrust of Bad Dog's case - which he makes very well.

The spindle bearings have to be in pretty bad shape to warrant replacement. Some wear on angular contact bearings can be taken up with pre-load adjustment.

If the machine seems OK - visual and "feel" then it would be good enough for me. Seeing it "run" would be better of course but as is often the case it may not be an option. Many of these machines are on offer on an "as is - where is" basis.

I bought new surface T&C grinders - for personal reasons and that there are or were none here that were within reasonable driving distance. I am limited by size as to what I could fit in.

Never-the-less my procedures were the same.

First, turn the motor over by hand and use "feel" to see if all seems OK and that there is no obvious or measurable "run-out" or bent shaft. Test "X", "Y" and "Z" ways, gibs, etc.

Next, spin the motor without a wheel on it and let it run for 30 minutes or so and re-check for "nasty noises" and rough running.

Mount a medium aluminium oxide wheel, dress it, balance it, re-dress it. If no balancing features are included, don't worry as grinding wheels are pretty well balanced anyway. Run it up and re-check for "noise" and "feel".

If all of the swept part of the table passes under the wheel, take a series of light cuts until there is only a "witness" (mark) left. The table has now been "trued" to the machine ways ("X" and "Y").

Place magnetic chuck (inverted - ie top down, bottom up) on table and lightly clamp (shim if needed) using the magnets. Grind the base of the magnetic chuck with light cuts - leave a "witness". The base of the magnetic chuck is now as flat as the machine ways/guides.

Reverse the magnetic chuck on the table (bottom down and clamped to the table, magnetic face up) and lightly grind - leaving a witness. The chuck is now "trued-up" to the machine guides and ways.

Mark the position of the chuck on the bed for future reference/mounting.

If the grinder is only going to have occasional use in the HSM shop and if accuracy of say 1 or 2 "tenths" (will probably be much better) is OK and if the grinder is used for "clean-ups" etc. where "parts of tenths" is not required, I would use what ever bearings were available.

So-called "cheap" or bearings from eastern Europe or Asia are very good indeed - and heaps cheaper.

Far too much is made of some of the exorbitantly priced "top of the range" bearings but for shorter less rigorous life-spans the lesser bearings are quite OK.

I could never see any grinder spindle bearings in my shop that could justify "industrial" or "heavy use" or required life of more than say 200 hours a year (4 hours a week average) with a reliability of better than 90%. That puts many very cost-effective cheaper bearings well within reach - if - and only if - the bearings needed replacement at all.

I get by very well with "handraulic" "X" feeding. Its no effort really. "Auto" or "power" mightr be nice to have but is certainly not in the "need to have" category.

Frankly, my surface and T&C grinders get very little use. I'd guess that would be the case in most HSM shops that have them.

Most of my grinding is done on a pedestal grinder or angle grinders. Ilike and do pretty well with hand and off-hand grinding.

If my lathe and mills are running OK, the effort of setting up the grinders is not worth it - most times.

Those grinders are a real asset on the occasions that they are needed though.

I have yet to see or see mention of a surface or T&C grinder in John Stevenson's shop and if there is anyone on this forum (that I know of) that is more expert than John in getting what he wants when he wants at pretty well "give-way" prices, I have yet to hear of it!!. If John can get by without them, it sort of weakens the case for having them

It is surprising (or is it??) just how "common" common sense isn't.

A good deep breath and a "sit down and think" first - before all else - is the way to to go - just as Bad Dog seems to be doing. As he says a real purpose-made grinder is well within reach - cheap.

ega
08-14-2008, 09:28 AM
I think your swing grinder picture may be from a series in Model Engineers workshop.

tdmidget
08-14-2008, 08:50 PM
This entire thread is rediculous. A radial saw would hard put to hold 1/32" ( .03225). A surface grinder worthy of the term should be able to grind to a flatness and size of .0002" with a finish of 16 microns or better. Merely putting a grinding wheel on a spindle doesn't make a grinder.

dp
08-14-2008, 09:11 PM
This entire thread is rediculous. A radial saw would hard put to hold 1/32" ( .03225). A surface grinder worthy of the term should be able to grind to a flatness and size of .0002" with a finish of 16 microns or better. Merely putting a grinding wheel on a spindle doesn't make a grinder.

That happens to be a load of crap, Midget. You've assumed far too much. It turns out I put a wheel on the radial arm saw spindle and using my spindexer was able to create a perfectly usable hex head on a specialty bolt I needed to make from scratch. It worked perfectly well and produced a product I'm happy with. I could have worked the same job on my mill but I can replace/true wheels easier than I can sharpen/replace end mills.

It was not necessary or even a consideration that I would grind anything to within .0002", only that I have a flexible and useful grinder. I have and I'm very happy with the results. But if anyone repeats this experiment I'd recommend getting the sawdust out of every corner of the saw, first.

But wait, there's more. I have a carbide scraper tool I bought from Forrest Addy. I needed to have something to dress it with, so I bored and faced a 5" iron round and mounted it to the radial arm saw. I applied some yellow diamond paste and dressed that scraper to a very fine finish. When I was done I put everything away. No need for yet another motor bolted to or sitting on a bench.

And more! Many years ago I bought a conical disk for my other radial arm saw. You apply sandpaper to it, tip it at an angle equal to the conical form, and do very nice surface sanding for small items. I got that out and cleaned up some 1/2" angle iron I'd cut off with my power hacksaw. Did a damn fine job.

And more, again. Years ago I bought some very nice clear cedar planking with the idea that I would make some bent wood boxes with it. Using an old grinder wheel cut to shape, I mounted it to the radial arm saw and ground a cutter for cutting the slots where the box edges bend. It worked perfectly.

Summary: By thinking outside the box I've discovered a very useful multipurpose tool for metal working and which in a pinch can be used for its original purpose: woodworking. It is a $40.00 radial arm saw. Just my .0002 cents.

Paul Alciatore
08-15-2008, 03:21 AM
Build a swing grinder from a cheap import drill press instead. It's on my list of things to do, still...

http://vts.bc.ca/pics/swinggrinder.jpg

Evan,

I must say I am intrigued by this idea. Can you provide any further information? Construction article or plans? Web site? Whatever?

I would imagine that bearings and alignment of the spindle is critical. Any other non obvious considerations?

small.planes
08-15-2008, 03:32 AM
It looks like a std bench grinder with one wheel removed bolted to a swinging arm, then the stub shaft for the other wheel covered with a tube guard, and a few measurey/tweaky handles added :)

Dave

radish1us
08-15-2008, 04:57 AM
It looks like a std bench grinder with one wheel removed bolted to a swinging arm, then the stub shaft for the other wheel covered with a tube guard, and a few measurey/tweaky handles added :)

Dave


You are 100 % correct with that lot and IT was in the Model Engineers Workshop series where I first saw it.

regards radish

radish1us
08-15-2008, 05:04 AM
For those that are after some information about this swing grinder, then get your grubby paws onto the Model Engineers Workshop # 45 Oct/Nov 1997 issue, it's ALL in that one issue, drawings and fairy tales as well.

regards radish

J Tiers
08-15-2008, 08:34 AM
Bad-puppy et al:

That 5 grand?

If you have a large SG with obsolete bearings, that might not be totally unreasonable...... There are bearings that are $900+ a pop, generally for larger spindles, and while 5 grand is probably an exaggeration, it might be off only 2:1 when all the various bearings are replaced (including table), and not "off" at all as a total if the ways are re-done.

Doubt many will pay that to re-build a big hunk o iron, unless they want something specific that particular item can do specially well. Not while Grizzly and Jet are around.

But I don't see how a wonderful, high quality used (and abused) machine can do a good job with "coggy" failing bearings that need replaced, sloppy feeds that don't repeat, etc. If you get a good one, and can move and fit it in, great.

Most people here can't, so since industry doesn't want the machine (they are selling it, remember) and home-shop folks don't, it goes for scrap, or sells cheap for shipment to the boonies of the 5th world.

A S-G is for putting a good surface, to-size, on a part. If it is so worn that it does little better than a mill, what's the point?

Sheesh...... If you can't MILL decently in a freakin drill press (and usually you can't in cheaper ones/ lighter ones) how the blue blazes is "surface grinding" going to work well?

The saw might do better, although most radial arm saws are loosey-goosey, and your only hope is that the mass of the head helps you out by steadying things.

But at least the saw bearings will hold the wheel more steady than a "cheap import drill press" (per a post above) which may not HAVE even two bearings in the quill, let alone decent quill slop, etc.


Why you seem to think there is such a huge difference between Sanford/Rockwell and BS/etc. 6x12 (or even 6x18) is beyond me...


Because, your tiny mind seems to have forgotten that there is a SMALLER Sanford. A 6 x 12, yeah I think they made one, ... but there is also a Sanford of about half that size. I want to say it is 4 x 6 or so. It goes for a premium, because it's easy to carry and fit in, and probably seems "non-threatening" as well.




I never said anything like that. Where you got "large" or "electric motor bearings" (much less $25) is beyond me. Funny how just a few lines later you start playing language lawyer after pulling this stunt, but that is very much in character.

Not only that, but where do you get off with cracks like "your home country"? Sad really...


Sad? I would agree..... the whole make-do deal of mounting a wheel on a stem in the drill press to do surface grinding IS a bit sad... couldn't agree more!

Sadder still after the pieces hit you in the face.....

I assumed (for purposes of discussion) you live somewhere else, in some "home country" where shops evidently give away perfectly good equipment..... I don't think there is any such place......

But you missed the irony of that.... sorry for exceeding your capacity.

Evan
08-15-2008, 09:27 AM
Paul,

John S. sent me that a few years ago. It's very straightforward and is just a bench grinder on a swing arm. A drill press column and lifting rack would be about right if bolted to a heavy plate. I wouldn't expect it to perform like a proper surface grinder but that isn't the purpose of a swing grinder. A swing grinder is for putting on a decent ground finish that is reasonably true and parallel to the other side and for that it should work well. It is obviously limited to small pieces.

The design in the picture is missing a very important part that would greatly improve the performance. It needs a counterweight to balance the entire swinging portion and eliminate column deflection as the weight of the grinder is shifted. The extra mass would also improve the grinding action as it would help to dampen the action and prevent chatter.

Alignment is important but the grinder can dress it's own table of course.

I forgot to mention that the grinder motor needs a thrust bearing to control end float in the shaft.

lazlo
08-15-2008, 11:34 AM
John sent me the swing grinder article from Model Engineer's Workshop a couple of years ago -- the one that Evan's picture is from. The main problem with it is, like Small.Planes says, is that it literally takes a bench grinder and hangs it on a vertical post.

A bench grinder usually has a single non-precision radial ball bearing (like a 6204) on each end, so it's not intended for axial thrust like you're going to get on a swing grinder.

So the bearing arrangement is going to be marginal at best, and I can't imagine you'd get any kind of decent surface finish with it.

http://i164.photobucket.com/albums/u15/rtgeorge_album/SwingGrinder.gif

JCHannum
08-15-2008, 11:56 AM
The swing arm grinder in Jon's photo is a bit more than a DE grinder mounted on a cheap drill press. The column and base from one might be a starting place, but it would be worthwhile to obtain the article in question to determine the rest of the story. It obviously has quite a few features that are not common to any drill press. (I see Lazo posted while I was typing and is able to comment on the content of the article.)

I seem to recall a contributor a couple of years ago who was making swing grinders for the drag racing crowd that were fairly simple, but accurate enough for flywheel grinding. I have not been able to locate the posts though.

Some of Jerry's comments about used surface grinders are correct. But the nature of the economy is such that good, serviceable HSM sized grinders are available on the market at affordable prices. Yes, the small Sanford commands a high price relative to the larger 6 X 12 machines, but it's usefulness is limited, and one is better off with a somewhat larger machine, a Rockwell toolmaker or one of the smaller KO Lee T&C grinders.

When considering adding a grinder to the shop, consideration must be given to the mess and abrasive dust created and locate them away from other tools. The footprint of those smaller grinders is not much more than that required by the bench a Sanford will need, so in reality, the Sanford offers little advantage.

biometrics
08-15-2008, 12:45 PM
Does the rest of the article mention a bearing change for the grinder to eliminate or reduce the thrust issues?

Thanks,
-John

lazlo
08-15-2008, 12:52 PM
Does the rest of the article mention a bearing change for the grinder to eliminate or reduce the thrust issues?

No.

Most of the article is about building the vertical column and the base. The vertical column has a thrust bearing so the pedestal grinder can "swing".

If anyone wants to take a look at the article, drop me a PM...

MickeyD
08-15-2008, 03:03 PM
I have one of the little 6x12 benchtop Taiwanese surface grinders, and I think that it is the absolute lowest you can go on the surface grinder scale and get a remotely usable machine that gives reasonable accuracy and a somewhat decent finish. If you just have to build your own, the 6x12's would be a good place to start.

TheAndroid
08-15-2008, 06:14 PM
So what would be considered "good" bearings for building one's own grinder? I have the Duclos book from VP and the article in there makes it seem like any other detailed project.

I looked on the Boca Bearings website and found 3/4 ID, stainless, sealed bearings with a high fit and ABEC rating (C54 and ABEC 7) for $85. Would these bearings be too sloppy for use?

I can get sealed ABEC 7 skate bearings all day long and build a small spindle to use those too. Here at AbateCo, we don't work with tolerances down to the wavelength of laser light. So for HSM use, I would think that would be fine.

lazlo
08-15-2008, 07:17 PM
So what would be considered "good" bearings for building one's own grinder? I have the Duclos book from VP and the article in there makes it seem like any other detailed project.

Do you mean the Glenn Wilson Tool and Cutter Grinder? According to the spindle drawings, there's a bearing front and back (like the Quorn), but he leaves out the dimensions and the type of bearing: "Press fit to selected bearings" :)


I looked on the Boca Bearings website and found 3/4 ID, stainless, sealed bearings with a high fit and ABEC rating (C54 and ABEC 7) for $85. Would these bearings be too sloppy for use?

A pair of angular contacts like those would be perfect. ABEC-5 is fine for HSM use. The Quorn spindle uses a pair of magneto bearings, which are Poor Man's angular contacts, equivalent to ABEC-1.


I can get sealed ABEC 7 skate bearings all day long and build a small spindle to use those too.

I don't think any skate bearings are really ABEC-7 or even ABEC-5. VXBearing sells "ABEC-7" skate bearings for $2 each on Ebay -- it's hard to imagine that they can hit the ABEC-7 50 microinch tolerances for a $2 bearing...

MickeyD
08-15-2008, 07:57 PM
Personally I don't think that the bearings are the big problem. I think that the big problem comes from flex and rigidity issues in the rest of the machine. You can have the smoothest spindle in the world but if it is mounted on the flexible flyer of homemade grinders you are going to get a bad finish and little control.

lazlo
08-15-2008, 08:06 PM
Dunno Mike -- a surface grinder is one of those machines where the bearing runout is going to reflect (literally) in the work. It's hard to hit a 32 - 16 RMS finish (typical "good" surface ground finish) on a workpiece if you have plain bearings with several tenths runout...

Evan
08-15-2008, 08:42 PM
Personally I don't think that the bearings are the big problem. I think that the big problem comes from flex and rigidity issues in the rest of the machine. You can have the smoothest spindle in the world but if it is mounted on the flexible flyer of homemade grinders you are going to get a bad finish and little control.


Much more important is wheel balance and wheel dressing for proper geometry (roundness, flatness etc). It doesn't matter how good the rest is if those are not correct, especially balance. A well balanced wheel will run smooth and quiet even on relatively "sloppy" bearings. Bearing slop in the tenths can be taken up in the fit of the bearing in the bore that holds it. A clamping arrangement can be easily devised that will compress the outer race enough to remove most clearance in a lower grade of bearing such as an electric motor grade part.

Of course there is the poor man's substitute for angular contact bearings, tapered rollers. NTN makes tapered roller bearings in a 15mm shaft size rated at 16,000 rpm.

MickeyD
08-15-2008, 09:28 PM
I am not saying that the bearings do not matter, what I mean is that the rest of the machine is going to have so much wiggle that it won't matter whether you have the right bearings or bearings out of an old roller skate. You are going to get a bad finish either way using a radial arm saw or a cobbled together piece of junk. Either get a real surface grinder (crufty looking serviceable ones often sell for less that scrap value) or lap by hand. For most of the hobby work that people of this forum do, hitting within a couple of thousandth is plenty accurate, but with a surface grinder you are talking about tenths, and that is another ballgame.

J Tiers
08-15-2008, 09:37 PM
and one is better off with a somewhat larger machine, a Rockwell toolmaker or one of the smaller KO Lee T&C grinders.

The "Toolmaker" puzzles me.

It sort of LOOKS like a radial arm saw conversion, designed by the Shopsmith company, and hybridized with a rail grinder. It just does not LOOK like it would do an acceptable job of knocking off the odd 2 tenths etc.

Are looks deceiving? Is the device actually a good and useful tool for use as a S-G?

JCHannum
08-15-2008, 09:41 PM
The "Toolmaker" puzzles me.


Are looks deceiving? Is the device actually a good and useful tool for use as a S-G?

Yes and yes.

The earlier version with the cast iron legs is somewhat spidery in appearance. The later version with the sheet metal base looks a little better, but both are good machines for their intended purpose.

The only disclaimer with both the Toolmaker and the KO Lee T&C grinders is that the statement is in the context of comparing them to the small Sanford SG. Their work envelopes are probably comparable, I would have to look them up, but the T&C grinders may have an edge in capacity.

The T&C grinders offer the added dimension of T&C grinding as well of course. I think the Sanford would be lacking in that department.

lazlo
08-15-2008, 10:01 PM
A well balanced wheel will run smooth and quiet even on relatively "sloppy" bearings. Bearing slop in the tenths can be taken up in the fit of the bearing in the bore that holds it.

How do you figure? If you're using ungraded bearings with a runout of say, 3 - 4 tenths, which is typical), no dressing or balancing in the world is going to fix that.


A clamping arrangement can be easily devised that will compress the outer race enough to remove most clearance in a lower grade of bearing such as an electric motor grade part.

Doesn't work that way Evan. Most quality bench grinders (i.e., Western ones) have a wave washer to take-up axial float and some of the internal clearance, but no preloading is going to make up for the actual bearing runout.


Of course there is the poor man's substitute for angular contact bearings, tapered rollers..

Tapered roller bearings are not Poor Man's angular contact bearings.

For a given size, tapered roller bearings are much more rigid than the equivalent ball bearing, which is why they're used in lathes. Tapered roller bearings come in accuracy specs up to ABEC-9. The only problem is that due to the linear contact angle on the rollers (instead of a point contact on a ball bearing), you have more friction, so they're not rated for high speeds like ball bearings.

Evan
08-15-2008, 10:32 PM
Doesn't work that way Evan. Most quality bench grinders (i.e., Western ones) have a wave washer to take-up axial float and some of the internal clearance, but no preloading is going to make up for the actual bearing runout.


I'm not talking about pre-loading or axial play. I'm talking about actually compressing the bearing outer race to take out radial clearance. It most certainly does work that way although unless you are in the habit of making press fits you may not realize it. I never use loctite on anything. I prefer to make the fit metal to metal and there have been times when it is a little too tight. You can feel it in the bearing as it has no radial play at all.

As for tapered bearings it does depend on what your needs are. For me 16000 rpm is good enough.

A well balanced and trued wheel will do a much better job on even low quality bearings as it won't be causing the entire assembly to vibrate and deflect. The slight amount of play will be taken up against the work and a reasonable finish can be had.

There is no arguing that the bearings in this cheap drill press head are less than the best by a lot but the wheel is top of the line and very well trued and balanced. The finish produced is very acceptable.

http://vts.bc.ca/pics/tpg1.jpg

lazlo
08-15-2008, 10:43 PM
A well balanced and trued wheel will do a much better job on even low quality bearings as it won't be causing the entire assembly to vibrate and deflect. The slight amount of play will be taken up against the work and a reasonable finish can be had.

Ah, I figured there was a reason you were sensitive on that comment. So you're saying that by pressing a common ungraded bearing into a press fit, that you're increasing the precision of the bearing? :)

The critical requirement on ABEC bearings is the runout of the inner and outer races with the center bore. That's how much wobble you're going to have with the wheel on the end of the bearing.

By compressing the outer ring, you may be able to reduce the clearance between the rings and the balls, but that's not going to improve that runout spec. Remember, the C2, C3 clearance (the internal clearance of the balls with the rings) is separate from the ABEC precision specs.

But I agree, with a well-trued wheel you can get an "acceptable" finish with ungraded and non-preloaded bearings, but there's a reason that toolpost grinders (and surface grinders) come with pre-loaded ABEC-7 (or better) bearings.

radish1us
08-15-2008, 10:49 PM
How do you figure? If you're using ungraded bearings with a runout of say, 3 - 4 tenths, which is typical), no dressing or balancing in the world is going to fix that.



Doesn't work that way Evan. Most quality bench grinders (i.e., Western ones) have a wave washer to take-up axial float and some of the internal clearance, but no preloading is going to make up for the actual bearing runout.



Tapered roller bearings are not Poor Man's angular contact bearings.

For a given size, tapered roller bearings are much more rigid than the equivalent ball bearing, which is why they're used in lathes. Tapered roller bearings come in accuracy specs up to ABEC-9. The only problem is that due to the linear contact angle on the rollers (instead of a point contact on a ball bearing), you have more friction, so they're not rated for high speeds like ball bearings.

Lazlo, dunno where you getting your speed ratings for bearings from, but single row tapered roller bearings are rated at about 2/3 rds the speeds of single row deep groove bearings, better go get your bearing book out and start checking, eh.
This particular swing grinder is made from a BENCH GRINDER, motor speed WOULD/COULD be only 1450 rpm or 2800 rpm, think about it, that's well with-in the tapered bearing specs, now don't you?
While your at it, go read the full article once again, you just so happened to post the photo of the first page of the article, which explains it all. Then it might sink in, that this swing grinder is NOT intended to do that ABSOLUTE perfect finish that YOU are after, or take off that last one thousands of a thou, that you seem to be looking for, so this simple idea DOES DO what it was designed to do, better go read it again before you reply to this.

regards radish

lazlo
08-15-2008, 10:51 PM
Lazlo, dunno where you getting your speed ratings for bearings from, but single row tapered roller bearings are rated at about 2/3 rds the speeds of single row deep groove bearings, better go get your bearing book out and start checking, eh

Uh, right. That's what I said: tapered roller bearings are available with the same precision as angular contact bearings, but they have a lower RPM rating because of the contact area of the roller. How is that different than what you're saying?


This particular swing grinder is made from a BENCH GRINDER, motor speed WOULD/COULD be only 1450 rpm or 2800 rpm, think about it, that's well with-in the tapered bearing specs, now don't you?

Yes, you absolutely can make a precision grinding spindle with tapered roller bearings. Harprit Sandhu has an excellent grinding spindle project on page 102 of his "Spindles" Workshop Practice book that uses tapered roller bearings.

I was referring to Evan's comment that tapered roller bearings were "poor man's angular contact bearings", which is decidedly not the case: tapered roller bearings are just as precise, and more rigid, than angular contact bearings.

radish1us
08-15-2008, 10:54 PM
Did you go read the rest of the page ?

lazlo
08-15-2008, 10:58 PM
Yes, I've read the article, several years ago, and again today. What's your point?

oldtiffie
08-15-2008, 11:49 PM
The "big Gorilla" is actually the dynamic balancing of the rotating motor and wheel spindles.

Without that being right the rest is a wasted of time.

Swing saws, mitre saws and that pic that Evan posted all rely on the operator swinging off the wheel movement system.

On any reasonable grinder everything - other than the wheel down-feed - moves relative to the wheel. (There are some exceptions - but not many).

Have you ever seen or can you imagine what might happen to the wheel or the job - and the operator - if the wheel "digs in"? It is not a pretty sight nor is it an experience you will forget easily.

Just try leaning on the motor or spindle casing when the wheel is cutting on an ordinary surface grinder - even very good ones - and see what happens. It will be much worse here.

Given all the recent discussion on the lack of stiffness in some less expensive vertical mills, do you seriously think that the vertical grinder that Evan posted will be any better? The more so as the operator has to move the whole assembly. Add to that that the "tramming" of that spindle to the magnetic chuck to get any reasonable accuracy over the whole table is not practical. Add to that the matter of the "side-wheeling" needed and there is going to be an awful lot of wheel contact. Not to mention the lateral forces on the work-pieces, the magnetic chuck (and it's ability - or lack of it - to cope with them) and there is a recipe for disaster.

I would forget about bearings and wheel balance until those problems were addressed and solved.

I once saw a grinder of this sort have an "incident". The work was on a magnetic rotary magnetic chuck (a really good one) and had a peripheral "fence" all around it. The grinder spindle was vertical and feed downward. The grinding wheel was in separate segments/pieces and was permanently over the rotating chuck. For what-ever reason, either one of wheel segments "let go" or one of the work-pieces "let go" and flipped into the segmented wheel in which two of the segments disintegrated and "flew" - all in a split second with a "bang" that could be heard all over the shop. The operator was, as I recall, a "Second-Class" machinist (you had to be really good to be a "First-Class" in "those days") was pretty good at his job. It was not his fault. It was "just one of those things". He asked for and got another job in the shop and nobody else wanted to use the grinder. It got very little use after that.

You cannot be too careful when it comes to surface grinding - or T&C, or cylindrical grinding - in any of their shapes and forms.

MickeyD
08-16-2008, 12:08 AM
Well said Tiffie. That is what I should have said earlier and would have said if I had not been drinking tequila all evening. I was recently using my surface grinder to knock about half a thou off of a couple of flat washers for shimming a DRO, and several of them were tossed off of my fine pole chuck because I tried to take .0002 off instead of .0001" at a time. Surface grinders will bite you when you get in a hurry.

oldtiffie
08-16-2008, 12:23 AM
Thanks MickeyD.

That is what the fences are for on magnetic chucks!!

If it were me with flat washers, I'd have used a thin steel strip as a "stop/fence" (an Engineer's 6" rule works fine) and put it on the chuck and put the washers up against it.

Two strips in the form of a "Vee" can be even better.

It sure wakes you up when that happens doesn't it?

Its too easy to almost get mesmerised or let your attention "wander" on a grinder.

MickeyD
08-16-2008, 01:06 AM
It was one of those deals where I was trying to take them down just a hair lower than my fence would hold them (washer thickness was .015) and my fence has been touched enough times over the years that it is now shaped like a little launch ramp that is about that high. The little washers did not have enough mass to hurt anything, but were a real pain to find after they went flying.

oldtiffie
08-16-2008, 01:58 AM
John sent me the swing grinder article from Model Engineer's Workshop a couple of years ago -- the one that Evan's picture is from. The main problem with it is, like Small.Planes says, is that it literally takes a bench grinder and hangs it on a vertical post.

A bench grinder usually has a single non-precision radial ball bearing (like a 6204) on each end, so it's not intended for axial thrust like you're going to get on a swing grinder.

So the bearing arrangement is going to be marginal at best, and I can't imagine you'd get any kind of decent surface finish with it.

http://i164.photobucket.com/albums/u15/rtgeorge_album/SwingGrinder.gif

Yep, as I said, I can see all of the problems I referred to.

There has been a lot of discussion the requirements for this and similar "grinders".

First of all, they are not precision grinders. The rotors are not dynamically balanced to "grinder" specifications. It is highly unlikely that "precision" bearings will be a "straight swap" - size for size. The end caps on the motor are unlikely to have the bearing pockets and retainers/locators machined to the equivalent of a BP quill cartridge either - and they may well not be able to be.

This "arrangement" might at best be OK for knocking off "bumps and snots" (only).

I'd think it would bea lot more than "easy" to fit a "wheel-balancing hub" (or arrangement) that will suffice for a precision grinder either.

I note that in the pic that there is a small but probably quite accurate Tool & Cutter grinder that could do well as a small T&C grinder with the magnetic chuck as well.

If I were knocking off "snots" etc. I'd be using my "Triton" vice and a good off-hand/angle grinder with a good wheel or "flap-wheel" to tear it off. It would get the job done well and safely and not spread grinding grit all over the shop.

For what its worth, I have very good "Made in the USA" "Bosch" 10" mitre-saw on a very good bench, so I am not unaccustomed to the vagaries, limitations and requirements in that regard either. Same for the "DeWalt" over-head saws as well.

Surface and tool grinding are areas where the "right tool for the job" is pretty well essential. It applies to any grinding actually.

lazlo
08-16-2008, 02:04 AM
I note that in the pic that there is a small but probably quite accurate Tool & Cutter grinder that could do well as a small T&C grinder with the magnetic chuck as well.

Yep, that's a Stent Tool and Cutter Grinder, as Norm will attest :) Very nice design, with a cartridge spindle with magneto or angular contact bearings. It's a casting kit that comes from Blackgates in the UK, so they're very rare in the 'States, but I've heard they work great as a little surface grinder.

Evan
08-16-2008, 04:25 AM
I get the impression that nobody is actually reading anything here, just writing. I wasn't aware that grinding was a religion. I thought that only applied to lubrication and vehicle makes.:rolleyes:

The swing grinder shown isn't some sort of bastard "make do" machine. It's a close copy of commercial equipment but with additional features. It does suffer from a couple of basic design flaws though.

Here is a commercial unit. It's a Rydal punch and die grinder.

http://vts.bc.ca/pics5/swing1.jpg

There are a couple of important differences. The most important is the geometry of the swing arm in relation to the wheel.

The shop built grinder will rotate around the approximate center of the grinder motor and it's column mount with the result that the wheel will describe an arc on the end of the grinder shaft. This will enhance the dig in as the wheel edges follow that arc toward the centerline instead of merely rocking around it as in the commercial unit. The forces produced will be from side to side as shown in the drawing in blue.

The commercial unit is designed so that the axis of rotation is aligned with the center of rotation of the wheel as shown in green. Digging in will produce forces primarily to and from the column which are well constrained and will not result in significant forces in the direction of swing.

http://vts.bc.ca/pics5/swing2.gif

The other shortcoming is the lack of balance. In the commercial unit this is in part obviated by the placement of the swing bearing on the column. It is below the center of rotation of the wheel. Again, this prevents any deflection from producing a reenforcing action if the wheel cuts too deep. Note the gib screw at the bottom of the swing bearing. This undoubtedly acts on an internal gib the takes up the slack at the bottom of the sleeve. This will act to make that point the center of rotation of the sleeve under deflection forces.

The shop designed unit can be easily redesigned to incorporate these simple changes and if so done will be safe to use.

JCHannum
08-16-2008, 08:24 AM
The Tiffster's comments are valid to this discussion. The shop made swing grinder has many areas of concern, and lack of attention to details and potential hazards could lead to problems. The problems could be as minor as poor surface finish and as major as personal injury.

There are purpose built swing grinders, and several have been mentioned in other posts. They do exist. They also are just that; purpose built; designed for the intended job with proper materials and construction.

The Rydal punch & die grinder is such a purpose built machine. There are other manufacturers of similar equipment, but they are very few and far between. That swing grinder configuration is not in common use as a surface grinder for very good reason.

Blanchard type grinders are in use, but they are massive machines of a very different construction, heavily guarded and given, at times, to the antics Tiffie described.

J Tiers
08-16-2008, 08:36 AM
The other shortcoming is the lack of balance. In the commercial unit this is in part obviated by the placement of the swing bearing on the column. It is below the center of rotation of the wheel. Again, this prevents any deflection from producing a reenforcing action if the wheel cuts too deep. Note the gib screw at the bottom of the swing bearing. This undoubtedly acts on an internal gib the takes up the slack at the bottom of the sleeve. This will act to make that point the center of rotation of the sleeve under deflection forces.

The shop designed unit can be easily redesigned to incorporate these simple changes and if so done will be safe to use.

I generally agree. The difference in workhead mounting is glaringly obvious.... clearly that Rydal was "designed".... not built by a "practical man".

Not ONLY that, but the column is evidently shorter and stiffer, AND the workhead wheel is a lot smaller in diameter than the "Jeeves" swing grinder. The general forces will lead to a lot less 'nodding" and dig-in potential.

The direction arrow on the arm is no doubt so that the "direction of throw" is towards the back. That makes the thing somewhat safer also.

The Rydal is intended for smaller parts, and is proportioned for them. Even then, it is more solid than the "Jeeves" grinder. The intended use seems to be punches and dies, which are usually relatively small round parts, which are ground generally flat on top, and are wanted sharp yesterday, making the swing design sensible. You can slap the parts in and grind them pretty quickly, by the look of it. Does it allow grinding a "shear" on the parts?

Possibly the "jeeves" grinder is partly "saved" by the mass of the grinder body. That will stabilize it somewhat

I think however, that if you look, the lower bearing area you refer to on the Rydal is merely a "hood" preventing grinding dust from striking the column. Due to vertical adjustment, that area is extended so it comfortably overlaps the column base and protects even if the workhead is raised a bit with the crank at top.

.

Peter Sanders
08-16-2008, 08:44 AM
Hi

I don't see why there is so much discussion of the "cons" (bad) aspect of this swing grinder. Personally I think it is quite a good device and would like to make one if it ever gets to the top of my todo list :)

Why there is so much reference to the "danger", "safety" and accuracy of this device is beyond me. We all work with equipment that has similar aspects of danger and safety. Those among us that would build such a device would surely be aware of all of the factors surrounding ANY kind of ginder use. I am also sure that swing grinder builders would not necessarily expect the same precise result as that of a accurately manufactured surface grinder.

By all means bring any shortcomings to the attention of prospective builders but lets not get carried away with the "cons" factor. Perhaps we could work toward resolving those shortcomings and more of us could have a useful extra tool in our workshops.

Evan
08-16-2008, 09:03 AM
Here is another similar style swing grinder complete with magnetic chuck.

http://vts.bc.ca/pics5/swing3.jpg

This is a different style of swing grinder. It hangs from a chain and movement is entirely controlled by the operator in direct competition with Newton's laws... To me it makes the above type look safe as houses.

http://vts.bc.ca/pics5/swing4.jpg


I think however, that if you look, the lower bearing area you refer to on the Rydal is merely a "hood" preventing grinding dust from striking the column. Due to vertical adjustment, that area is extended so it comfortably overlaps the column base and protects even if the workhead is raised a bit with the crank at top.


I am pretty sure that is a gib screw that is used to tram the head. That will place it as the main point of friction for the bearing to deflect and move around under load.

J Tiers
08-16-2008, 09:14 AM
I am pretty sure that is a gib screw that is used to tram the head. That will place it as the main point of friction for the bearing to deflect and move around under load.

Might be.

It LOOKS like it is offset to the right, which would put it offset around the column from the forces.

And,if there is any force when grinding, it is UP on the end of that arm..... so the resisting area of a bearing would be BEHIND the column.

If then the adjustment were in front, it could properly position the tram, but could NOT resist any up force due to grinding. After any wear, there would be a slop in the "up" direction which could not be adjusted out.

But, aside from a movement stop, there isn't much other reason for it, although it looks rather crude....

JCHannum
08-16-2008, 10:49 AM
By all means bring any shortcomings to the attention of prospective builders but lets not get carried away with the "cons" factor. Perhaps we could work toward resolving those shortcomings and more of us could have a useful extra tool in our workshops.

Surface grinding and the various configurations of surface grinders have been with us for years. Industry chooses it's tools based on performance and economics, balancing ccosts and results.

If there were a major advantage to be had with swing grinders, the economy of their manufacture would result in their being a very common tool rather than the exception that they are.

The main disadvantage is the nature of the swing itself. It sweeps an area, which limits the size of the workpiece to the very small area covered by the wheel and the swing. The nature of the swing itself imparts a radial grind pattern in the finished part. The radius of the swing precludes grinding anything but flat surfaces, making it impossible to grind any straight details such as V grooves or the side of a straight raised area.

The orientation of the grinding wheel is such that any little out of tram will result in a scalloped surface, not a flat one.

The safety aspects are self evident, the 360 degree danger zone of the wheel opposed to the relatively linear danger zone of a SG, which is much easier to guard.

In short, if a small SG is desired, a cheap drill press might be a place to look for a donor base, column and perhaps a start for a workhead, but one would be much better off applying his efforts to designing something more along the lines of a traditional SG and add a moving table, perhaps on linear bearings. The additional time spent will result in a much more useful machine.

lazlo
08-16-2008, 10:56 AM
clearly that Rydal was "designed".... not built by a "practical man".

Likewise. I wasn't criticizing a swing grinder as a design -- they're mini Blanchard grinders. There are Italian and Swiss "Swishers" (swing grinders) that are extremely well designed and made, and there are plenty of the benchtop variety that show up on Ebay.

My point is that a pedestal grinder is meant for grinding on the face of the wheels and not the sides -- radial forces, not axial forces like you'll get if you stand the pedestal grinder on its end. Pedestal grinders don't have precision bearings to begin with, so you're creating a worst-case scenario for the pedestal bearings.

If you really want to build a Swisher/Swing Grinder, you might consider mounting a toolpost grinder on the vertical column. A toolpost grinder isn't meant for axial grinding either, but they have a cartridge spindle with a pair of preloaded precision angular contact bearings, so they'll be able to handle a decent axial grinding load.

But honestly, you'll still have all the limitations that JC Hannum mentioned above. If I were going to cobble together a small surface grinder, I'd take a toolpost grinder and mount it above an x-y table, like that Stent T&C grinder in the MEW picture.

tdmidget
08-16-2008, 10:57 AM
That happens to be a load of crap, Midget. You've assumed far too much. It turns out I put a wheel on the radial arm saw spindle and using my spindexer was able to create a perfectly usable hex head on a specialty bolt I needed to make from scratch. It worked perfectly well and produced a product I'm happy with. I could have worked the same job on my mill but I can replace/true wheels easier than I can sharpen/replace end mills.

It was not necessary or even a consideration that I would grind anything to within .0002", only that I have a flexible and useful grinder. I have and I'm very happy with the results. But if anyone repeats this experiment I'd recommend getting the sawdust out of every corner of the saw, first.

But wait, there's more. I have a carbide scraper tool I bought from Forrest Addy. I needed to have something to dress it with, so I bored and faced a 5" iron round and mounted it to the radial arm saw. I applied some yellow diamond paste and dressed that scraper to a very fine finish. When I was done I put everything away. No need for yet another motor bolted to or sitting on a bench.

And more! Many years ago I bought a conical disk for my other radial arm saw. You apply sandpaper to it, tip it at an angle equal to the conical form, and do very nice surface sanding for small items. I got that out and cleaned up some 1/2" angle iron I'd cut off with my power hacksaw. Did a damn fine job.

And more, again. Years ago I bought some very nice clear cedar planking with the idea that I would make some bent wood boxes with it. Using an old grinder wheel cut to shape, I mounted it to the radial arm saw and ground a cutter for cutting the slots where the box edges bend. It worked perfectly.

Summary: By thinking outside the box I've discovered a very useful multipurpose tool for metal working and which in a pinch can be used for its original purpose: woodworking. It is a $40.00 radial arm saw. Just my .0002 cents.
"Load of crap"?. Reconsider. The fact that you put an abrasive wheel on a radial arm saw and produced a part that you were happy with does not make it a surface grinder. you might also put such a wheel on your lawn mower but it will STILL be a lawn mower, not a surface grinder. I gave you reasonable expectations for machines normally sold and used as surface grinders. No radial arm saw can do that. One of the most irritating aspects of this forum is that HSMs don't want to actually be machinists, they want to reduce the skill levels and machine nomenclature with cockamamie crap like hanging a grinding wheel on anything that rotates and suddenly it's a grinding machine.

Evan
08-16-2008, 11:13 AM
In short, if a small SG is desired, a cheap drill press might be a place to look for a donor base, column and perhaps a start for a workhead, but one would be much better off applying his efforts to designing something more along the lines of a traditional SG and add a moving table, perhaps on linear bearings. The additional time spent will result in a much more useful machine.


I agree with you Jim so I just cooked up a basic working plan for a swing grinder that owes nothing to cheap equipment. Using a very thick plate for the base and a low aspect large diameter column it will not be susceptible to deflection easily. The bearing would be another section of heavy wall pipe that would cover the column full length with a jack screw for adjustment. A mass of lead or other weight would balance the grinder on the rear with all parts heavily made and gusseted.

Three gib screws at the bottom of the bearing tube would serve to adjust tram. Other details would need to be filled in but this would serve as a good start, in my always humble opinion. ;)

http://vts.bc.ca/pics5/swingplan.jpg

dp
08-16-2008, 11:19 AM
"Load of crap"?. Reconsider. The fact that you put an abrasive wheel on a radial arm saw and produced a part that you were happy with does not make it a surface grinder.

It made a "poor man's surface grinder", an otherwise undefined term but generally indicative of a home made, good for some purposes item. So far it's doing everything I try to my satisfaction but I'm clearly cherry picking what I try. If this were PM I'd have never mentioned it, but this is HSM where a lot of clever people create solutions appropriate for home shop scale and budgets. Torker's climbing spikes come to mind :). This grinder solution is absolutely not a surface grinder in the classic sense, and even in a tortured definition it's still short. But it works, none the less, far better than I'd have imagined and I'm very glad I experimented with it.

Yesterday I used my spindle sander to shape the end of some steel tubing so I could weld it to another piece of tubing. I'm not ready to call myself a steam fitter but I did like the results.

All I'm doing is using common tools in uncommon ways and the results are surprisingly good and I'm having fun doing it.

Paul Alciatore
08-16-2008, 03:02 PM
Ah, I figured there was a reason you were sensitive on that comment. So you're saying that by pressing a common ungraded bearing into a press fit, that you're increasing the precision of the bearing? :)

The critical requirement on ABEC bearings is the runout of the inner and outer races with the center bore. That's how much wobble you're going to have with the wheel on the end of the bearing.

By compressing the outer ring, you may be able to reduce the clearance between the rings and the balls, but that's not going to improve that runout spec. Remember, the C2, C3 clearance (the internal clearance of the balls with the rings) is separate from the ABEC precision specs.

But I agree, with a well-trued wheel you can get an "acceptable" finish with ungraded and non-preloaded bearings, but there's a reason that toolpost grinders (and surface grinders) come with pre-loaded ABEC-7 (or better) bearings.

I usually argue with Evan, but in this case, I think he has a valid point. Consider, on a grinder the wheel is dressed (balanced) after being mounted on the machine. Removing the wheel generally necessitates redressing it as it is virtually impossible to remount it to tenths precision. This is in the nature of the wheels.

So if a bearing is compressed to take out the play but still run, it may be off center by a few tenths. This is true. And the shaft will be off center by a few tenths. But so what? The shaft has a very small radius compared to the wheel and it's unbalanced moment is going to be very small. A blob of grease on the exterior of the shaft or a small ding in it may produce as much or more wobble.

Now the wheel is going to be trued/balanced in place on that slightly off center shaft and will run as true as a wheel on a completely true shaft. There will be no difference in the two wheels.

I would be more concerned about any irregularities in the bearing races which would produce a regular disturbance and not any slight lack of concentricity.

Another thought (completely divorced from the above): If a bench grinder is used for a drill press swing grinder, you have the unused top shaft sticking up. Additional bearings, perhaps thrust bearings or a combination of thrust and radial, could easily be mounted there to help control the shaft play.

Evan
08-16-2008, 03:17 PM
Additional bearings, perhaps thrust bearings or a combination of thrust and radial, could easily be mounted there to help control the shaft play.


Or magnets....

w4bar
08-16-2008, 06:30 PM
I just waded through all 10 pages, and quite possibly missed the part where somebody answered the original question
"Anyone tried using a modified radial arm saw for a surface grinder? "

Well, I did. I've got a 60's era sears 10" that has been used and abused over the years, but still manage to restore an old house, build kitchen cabinets, a cradle, honey doos and surface grind a few peaces of steel. Everything that has been said about poor alignment is true.
I was young and foolish then and needed to put a decent finish on all surfaces of a couple of 1x3x5 plates. There was nothing precision about it, just clean up the surface. They were well clamped, depth of cut was small as possible. The results were quite good but the process was a hair raising one, especially when the "well clamped" work was spit off the table.

Would I do it again? If I had too and didn't value the saw too much and didn't have any other way. I would sure try harder to find another way.

Bob, much older and wiser now

lazlo
08-16-2008, 06:38 PM
So if a bearing is compressed to take out the play but still run, it may be off center by a few tenths. This is true. And the shaft will be off center by a few tenths. But so what? The shaft has a very small radius compared to the wheel and it's unbalanced moment is going to be very small.

I would be more concerned about any irregularities in the bearing races which would produce a regular disturbance and not any slight lack of concentricity.

There are two issues here: the first, the claim that compressing the outer race by press-fitting the bearing is going to improve the precision of the bearing, which is wrong, IMHO. All that's going to do is reduce the internal clearance of the balls with the races -- essentially making a C3 bearing into a C2. The internal clearance of the bearings has no relationship with the precision of the bearing, which is why it's common to buy ABEC-7 or ABEC-9 spindle bearings with C3 clearance -- greater than normal internal clearance*.

This is the ABEC table of dimensional requirements for precision angular contact bearings. Notice that internal clearance is never mentioned. What is specified is the runout of the inner and outer races with respect to the bore, and for ungraded (not even ABEC-1), that runout is typically in the ~ 3 tenths realm for Western bearings. For Chicom bearings, who knows:

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABEC2.gif

The second issue, that you can dress out the runout of the spindle, is partially true, but not nearly the panacea that Evan is claiming. Take, for example, the Harbor Freight carbide grinder that many of us, including you Paul (IIRC) have. These grinders have the same 6204 radial bearing that's in Evan's drill press, and almost all of these grinders have a huge amount of wobble out of the box. After extensively dressing the thick, plate-mounted wheels, I found that no amount of dressing was going to make a substantial improvement in the runout. If you search through the many HF grinder threads, you'll find that experience has been reported here many times. The only "fix" is to take off the wheels, and true the motor shaft, the shaft spacer, and the mounting plates. Any remaining wobble can be reduced by aggressively dressing the wheels, but it'll never run like the Baldor grinder.

*C3 (additional) internal clearance is usually specified for high-speed bearings, because the balls heat up considerably at high speed and will jam a bearing with CN or C2 clearance.

lazlo
08-16-2008, 07:13 PM
From the NTN Bearing Handbook:

Does internal clearance effect the bearing precision?
http://www.ntn.ca/faq.htm#clearprecision

Internal clearance is the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the NTN suffixes: C1, C2, C3, C4 and C5, where no suffix indicates normal clearance. C1 is a range less than C2. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4.

Precision is a range of tolerance on bearing dimensions. ISO and ABMA govern the precision ranges. ISO uses Class 0, Class 6, Class 5, Class 4, and Class 2 and ABMA uses ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively the systems are generally interchangeable. NTN uses P0 (usually not added to the part number), P6, P5, P4 and P2 to denote Class 0, Class 6, Class 5, Class 4 and Class 2, respectively.

Ultimately, clearance does not affect tolerance and tolerance does not affect clearance

wierdscience
08-16-2008, 09:46 PM
I agree with you Jim so I just cooked up a basic working plan for a swing grinder that owes nothing to cheap equipment. Using a very thick plate for the base and a low aspect large diameter column it will not be susceptible to deflection easily. The bearing would be another section of heavy wall pipe that would cover the column full length with a jack screw for adjustment. A mass of lead or other weight would balance the grinder on the rear with all parts heavily made and gusseted.

Three gib screws at the bottom of the bearing tube would serve to adjust tram. Other details would need to be filled in but this would serve as a good start, in my always humble opinion. ;)

http://vts.bc.ca/pics5/swingplan.jpg

Evan,I recently rebuilt the spindle on a automotive head surfacing machine.The spindle was butt simple,it was a shaft supported by two tapered roller bearings spaced about 6" apart.The preload was set by a spindle lock nut and four bellville spring washers.Spindle ran on white lithium grease and was over 15 years old.The top bearing only died after the new owner missed it's grease fitting repeatedly.

I also have at work something very similar to what you have designed.It's basically a small blanchard grinder,the head swings into position and locks in place while the work revolves on an electromagnet.

We use it to surface flywheels,steam flanges and plastic pelletizer dies.It runs a 5" diameter diamond face wheel.The actual width of the diamond grinding face is 3/8" wide.

The machine does a fine job,but cutting depth is limited to .0001" per rev.max.

Reason being the contact area of the wheel with the work piece is much greater than on a normal vertical wheel grinder.As a result the the forces involved are much greater.


I don't see any problem so long as a fine depth control adjustment is provided.

lazlo
08-16-2008, 09:56 PM
The spindle was butt simple,it was a shaft supported by two tapered roller bearings spaced about 6" apart.The preload was set by a spindle lock nut and four bellville spring washers.

Something like this (in the center)? :)

http://ecx.images-amazon.com/images/I/41F4E9KMMEL._SS500_.jpg


I don't see any problem so long as a fine depth control adjustment is provided.

Well, he's missing the most important detail: the spindle design.

J Tiers
08-16-2008, 10:12 PM
Something like this (in the center)? :)

Well, he's missing the most important detail: the spindle design.

Mebbe so..... but at least the spindle problems are limited to various camming errors when operating off the front of the spindle.... eccentricity is not an issue, the thing swings, after all.

That fact makes it a sensible machine.

But I still don't like it with large mounted wheels. That Rydal has a sensible size wheel for its size. The bench grinder kludge has a big wheel, and may be a big problem.

As far as the dressing as panacea..... I also disagree, as far as small errors are concerned.....

While the races are permanently (aside from creep) alined, the balls are not. So since a lesser grade bearing may likely have different sized (less well matched) balls, there may be a recurring error at the ball pass frequency, AND at the separator rotation frequency.

Are they small? Sure (we hope). But they are not possible to dress out of the picture.

lazlo
08-16-2008, 10:26 PM
As far as the dressing as panacea..... I also disagree, as far as small errors are concerned.....

No question that dressing a wheel will correct minor runout errors. But it ain't going to turn a Chicom radial bearing (ABEC -100, as Evan likes to say) into a precision angular contact bearing :)

dp
08-16-2008, 10:29 PM
Good grief - 100 posts about grinding. Is there an abrasive machining forum needed? Much of this thread seems overly abrasive :)

oldtiffie
08-16-2008, 10:38 PM
Why not by-pass all this kludge, buy a small Asian mill-drill with a belt drive and a reasonable spindle cartridge, "up" the spindle speed, tram the spindle to the mill table, put about 1/4 (or less) arc degree "tilt" on the milling head, put a cheap magnetic chuck on the table, fit a serviceable power feed (with a good rapid traverse) to "X", dress the wheel, take a cut across the chuck and away you go.

Use a cup wheel.

The wheels "as supplied" are pretty good as regards balance - so don't worry about it. Its usually only good surface grinders that have wheel-balancing anyway. Tool & Cutter grinders get away without it - and do very well as surface grinders.

With this set-up you should be able to get a quite acceptable finish and accuracy as good as the mill ways and table have (which should be very good).

A cut depth of up to a "thou" with a cross feed of up to 50 "thou" should be quite possible and acceptable.

Worried about the "curves" due to the "out of tram"? Don't. If you have a 6" wheel the difference is minimal. Reduce the cross feed per cut if you like.

So you get a reasonable surface grinder out of that "ChiCom junk"??? mill-drill after all.

"Vertical" cuts can be made by dressing the wheel using the milling head or quill down-feeds.

A little (a lot really) more lateral and creative thinking here will/may?? be a big help. Just "gnawing away" at something by way of argument instead of discussion or debate and conceding nothing just for the sake of "winning by attrition" (aka" the "last man standing is the winner") is hardly edifying.

lazlo
08-16-2008, 10:46 PM
Why not by-pass all this kludge, buy a small Asian mill-drill with a belt drive and a reasonable spindle cartridge, "up" the spindle speed, tram the spindle to the mill table, put about 1/4 (or less) arc degree "tilt" on the milling head, put a cheap magnetic chuck on the table, fit a serviceable power feed (with a good rapid traverse) to "X", dress the wheel, take a cut across the chuck and away you go.

I think that's a great idea Tiffie. There's an old HSM article about using a Mill/Drill as a surface grinder in much the same way. More recently, "Hossmachine" (a member here) did just what you describe with his Sieg X2 Mill. He's got a thread here somewhere about the build:

http://www.youtube.com/v/QIg1qC3wl-E&

dp
08-16-2008, 10:49 PM
Tiffie - In my case I have a limited amount of room so am trying to find adequate solutions by using what I have on hand. As cramped as I am now, when I move to my retirement abode I'll have even less room so I'm squeezing as much capability as I can from what I have.

Turns out there's a number of ways to achieve adequacy with a grinder, depending on the accuracy needed and the work size. I found my radial arm saw is somewhat ok as a grinder when passing the wheel over the work, but far better when passing the work under the wheel using a simple x-y table like you have.

I've also discovered it's really nice as a grinder for courser work such as prepping angle iron and pipe/tubing for welding or cleanup after hacksawing by using angle grinder disks. It works extremely well when using a wire wheel and passing the wheel over the work. That was a nice surprise. I'm going to put a sheet of steel over the existing MDF deck and see if I can keep the smouldering to a minimum :)

I'm quite happy with what I've learned from playing with this otherwise sacrificial saw. Turns out it's a damn good saw, too!

lazlo
08-16-2008, 10:52 PM
I found my radial arm saw is somewhat ok as a grinder when passing the wheel over the work, but far better when passing the work under the wheel using a simple x-y table like you have.

That's good to know DP, and it seems intuitive -- you would think that the overarm on the radial arm saw probably has a couple of thou movement, so keeping the saw head still would eliminate that.

What kind/size wheel did you use?

dp
08-16-2008, 11:05 PM
I bought a bunch of mystery wheels at the Boeing surplus in Seattle and the labels are mostly gone. I kept the ones that have the RPM visible and broke up the rest (was a batch purchase - good with the bad). They range from a very nice but worn small 4" wheel to 8". I have some cups but haven't made adapters yet. I'm getting good at turning inside left-hand threads, but I think I'm going to make a master adapter that will allow adding spacers vs turning one/wheel.

The grit is also a mystery but some are red, some are white, some are gray. The red wheels I wish I'd gotten more of. They produce a mirror surface even on my bench grinder. They're also somewhat soft so I'm going to save them for HSS cutters. Also picked up several India stones while there. I'm going to miss that place.

oldtiffie
08-16-2008, 11:05 PM
Thanks lazlo.

That is really automating it - CNC and all. I bloody near choked when I saw it was a "Seig" X3 mill as I'd hardy hardly classify that as "junk".

Another thing I hardly ever (never) see mentioned here is a guard/stop to catch any-thing from the wheel or the job - sparks and grindings - and occasionally some thing more substantial if anything - on the table/chuck or the wheel "lets go".

On my surface grinder it is cast iron/aluminium (haven't checked) on my "X" way covers - in the line of any residue.

I sometimes put a damp/wet rag over it as that catches the sparks etc. very well - it "captures" them (they stick to it) as opposed to just "bouncing" as is the case with the metal guard. All I have to do when it suits is to rinse the rag and have it damp for when I need it. It only takes seconds to put it place and it sure does limit the amount of grinding residues flying/floating and settling on anything and everything in the shop.

J Tiers
08-16-2008, 11:05 PM
No question that dressing a wheel will correct minor runout errors. But it ain't going to turn a Chicom radial bearing (ABEC -100, as Evan likes to say) into a precision angular contact bearing :)

Say what? I think I said the reverse of what you assumed.....

Actually, it probably WILL correct the bigger errors, most of the way...... but will LEAVE the smaller ones uncorrected. And of course won't deal with vibration issues......

I think we are agreeing.......

Truing can correct consistent once-per rev issues, at least partway.

Truing CANNOT correct periodic errors with a repeating pattern frequency not equal to once-per rev.

The latter will probably be quite noticeable when looking at a cheap bearing, especially a cheap bearing in a cheaply made product, like a cheap drill press, or a cheap grinder.

Noticeable when looking at a "grinder scale" of issues, which to me is stuff that goes from a couple thou down as far as you like.

Now, I want a grinder to deal with things of that scale, and make them go away..... smooth finish to settable and predictable tenths of tolerance. I strongly doubt that a DP or re-purposed cheap bench grinder will do that, except by chance.

However, if you want a ground finish to tolerances of 0.005 to a couple thou or so, there is no reason a cobbled-up grinding system cannot get to that area of tolerance, with a "ground finish".

dp
08-16-2008, 11:16 PM
you would think that the overarm on the radial arm saw probably has a couple of thou movement, so keeping the saw head still would eliminate that.
On this point I'm going to put my granite surface plate under the arm and check that out. I did a major cleanup of the raceways and bearings to minimize that, and have the head tighter than I would for just woodwork. After tramming it I can pass over a (edit) wet page torn from the yellow pages without snagging it. Clearly stationary is best.

What became obvious shortly after playing with it is that with the x-y table, the spindexer, and the capability of the saw to put the wheel at any compound angle, some very interesting possibilities were revealed. I restored a badly abused end mill (not including the flutes).

I should probably take some pictures. I'd purchased a Harbor Fright grinder a week before I bought the radial arm saw and I'm having more fun with the saw than the grinder. Need to replace the wheels on that one as the ones that come with it might as well be made from concrete.

dp
08-16-2008, 11:41 PM
I think that's a great idea Tiffie. There's an old HSM article about using a Mill/Drill as a surface grinder in much the same way.

Oh no!.... Now I have to get a mag chuck. What to tell the wife...

I Use a bunch of button magnets to catch most of the dust and sparks. Amazing how much stuff comes off that wheel. Well, I think I catch most of it.

Evan
08-17-2008, 12:22 AM
The second issue, that you can dress out the runout of the spindle, is partially true, but not nearly the panacea that Evan is claiming.

It seems you are operating on the principle that if you say something untrue much later in the thread people will think it is so. I never said any such thing. All I said is that it will take out some of the slop. You are making it sound like I said or implied that a cheap bearing can be turned into a high quality bearing by compressing it. Not so. It can just be turned into a bearing with less radial play.

As for spindle design, it isn't "missing". I haven't even considered it yet. I drew that up in a few minutes to illustrate a safe geometry for the machine. It isn't a construction plan. Stick to the facts Robert.


No question that dressing a wheel will correct minor runout errors. But it ain't going to turn a Chicom radial bearing (ABEC -100, as Evan likes to say) into a precision angular contact bearing


Are you in the habit of lying all the time Robert? It may be treatable.

oldtiffie
08-17-2008, 01:36 AM
Oh no!.... Now I have to get a mag chuck. What to tell the wife...

I Use a bunch of button magnets to catch most of the dust and sparks. Amazing how much stuff comes off that wheel. Well, I think I catch most of it.

Nah - don't tell her - go and do it! Let her find out for herself!! Let her see you for what you really are!!

Assert yourself - let her see you like this!
http://i200.photobucket.com/albums/aa294/oldtiffie/Funnies/Grilla1-1.jpg

If you are REAL lucky she will see you like this!!:
http://i200.photobucket.com/albums/aa294/oldtiffie/Funnies/Eatyourcereal.jpg

And if you are still able to read .....................


Amazing how much stuff comes off that wheel. Well, I think I catch most of it.

Ferrous stuff, perhaps. Wheel particles (aluminium oxide, silicone carbide) - not likely - tungsten carbide either. The "damp rag" gets most of it.

lazlo
08-17-2008, 01:40 AM
It seems you are operating on the principle that if you say something untrue much later in the thread people will think it is so. I never said any such thing.

Ah, but you did say those things Evan:


A well balanced wheel will run smooth and quiet even on relatively "sloppy" bearings.

Which most here agree is completely wrong. Truing the wheel can partially correct some consistent once-per rev issues.
But as Jerry said it best:


Truing CANNOT correct periodic errors with a repeating pattern frequency not equal to once-per rev.

The latter will probably be quite noticeable when looking at a cheap bearing, especially a cheap bearing in a cheaply made product, like a cheap drill press, or a cheap grinder.



All I said is that it will take out some of the slop. You are making it sound like I said or implied that a cheap bearing can be turned into a high quality bearing by compressing it.

And you said exactly that too:


Bearing slop in the tenths can be taken up in the fit of the bearing in the bore that holds it.

But as I explained, supported by a quote from the NTN Bearing Handbook, all you're doing is compressing the outer ring, which does absolutely nothing to improve the precision of the bearing.


As for spindle design, it isn't "missing". I haven't even considered it yet. I drew that up in a few minutes to illustrate a safe geometry for the machine. It isn't a construction plan. Stick to the facts Robert.

My point was that Wierdscience was "blessing" your design, but you haven't done the hard part yet: the spindle.

lazlo
08-17-2008, 01:48 AM
ABEC -100, as Evan likes to say

Are you in the habit of lying all the time Robert? It may be treatable.

http://bbs.homeshopmachinist.net/showthread.php?p=291304&highlight=ABEC negative 5#post291304


Note that of course the spindle bearings are probably ABEC negative 5 or similar. It does an acceptable job for things like removing mill scale with minimum reduction in diameter and in particular the grinding of counterbores which saved the expense of the drill press the first time I used it.

Evan
08-17-2008, 01:54 AM
[quote]Quote:
Originally Posted by Evan
It seems you are operating on the principle that if you say something untrue much later in the thread people will think it is so. I never said any such thing.


Ah, but you did say those things Evan:

No, I didn't.
Quote:
Originally Posted by Evan
A well balanced wheel will run smooth and quiet even on relatively "sloppy" bearings.
True

Which most here agree is completely wrong. Truing the wheel can partially correct some consistent once-per rev issues.

It isn't wrong at all. I do it, it works. It isn't a substitute for decent bearings and I didn't say it was.

But as Jerry said it best:


Quote:
Originally Posted by JTier
Truing CANNOT correct periodic errors with a repeating pattern frequency not equal to once-per rev.

That is true but only if it exists. Exactly where would periodic errors that are not directly related to revs come from in a direct drive system??? The fact that a bearing isn't precision doesn't mean it will always display such problems. I didn't say anything to the contrary either.

The latter will probably be quite noticeable when looking at a cheap bearing, especially a cheap bearing in a cheaply made product, like a cheap drill press, or a cheap grinder.
All I said is that the finish is acceptable, as you can see in the photo it doesn't look like it was hacked with an axe nor does it have any patterns at all.



Quote:
All I said is that it will take out some of the slop. You are making it sound like I said or implied that a cheap bearing can be turned into a high quality bearing by compressing it. Not so. It can just be turned into a bearing with less radial play.


And you said exactly that too:


Quote:
Bearing slop in the tenths can be taken up in the fit of the bearing in the bore that holds it.

Also true. I didn't make any claims about precision as you are implying.


Quote:
As for spindle design, it isn't "missing". I haven't even considered it yet. I drew that up in a few minutes to illustrate a safe geometry for the machine. It isn't a construction plan. Stick to the facts Robert.


My point was that Wierdscience was "blessing" your design, but you haven't done the hard part yet: the spindle.

I haven't done any part yet. That is only a concept drawing.
__________________
Get 'R Done. Right.


Now, about the part where you claim that "ABEC 100" is my favorite expression. Care to try and substantiate that?

Post 113 serves to illustrate exactly what? That I know the bearings are cheap? They should be, the drill press cost $30.

lazlo
08-17-2008, 02:10 AM
You don't see any contradiction between your earlier quote:


A well balanced wheel will run smooth and quiet even on relatively "sloppy" bearings.

and this latest one?


I do it, it works. It isn't a substitute for decent bearings and I didn't say it was.

Isn't "running smooth and quiet even on relatively sloppy bearings" saying that "it's a substitute for decent bearings"? :rolleyes:


All I said is that it will take out some of the slop. You are making it sound like I said or implied that a cheap bearing can be turned into a high quality bearing by compressing it.

I didn't make any claims about precision as you are implying.

You re-quoted your own comment :)


Bearing slop in the tenths can be taken up in the fit of the bearing in the bore that holds it.

Evan
08-17-2008, 02:56 AM
Isn't "running smooth and quiet even on relatively sloppy bearings" saying that "it's a substitute for decent bearings"?



No. Smooth and quiet is what you get when something is balanced and true regardless of what it has for bearings. Rough and vibrating is what you get when it isn't balanced and true, regardless of what it has for bearings. Simple.


You re-quoted your own comment

For your benefit. You emphasized "in the tenths". It's obvious that you didn't understand my point. The point is that compressing the outer race can only remove about that much clearance and not more. If the bearing has more clearance than that then after removing a few tenths worth of slop it will still have some left, but it will be less.

SO, exactly where did you get the ABEC-100 comment from?

oldtiffie
08-17-2008, 03:17 AM
If someone lets of go the rope that is holding you two in an ever- increasing velocity in the circular path (argument) you are having both of you will fly off at (another??) tangent and disappear into a big black hole.

Just like the Dodo bird, which according to legend flew faster and ever faster in ever-decreasing circles and disappeared up his own (fundamental) "black hole" (aka ar$e).

Sparks off a grinder are the only relevant tangents here - "knocking sparks" off each other isn't.

Evan
08-17-2008, 03:22 AM
I'm sorry for the distraction Oldtiffie but I won't stand for having my postings twisted and warped to mean something I didn't mean or say ( or write).

Paul Alciatore
08-17-2008, 03:33 AM
First, I still stand by what I said above. I don't believe that you can correct all of the problems of a lesser bearing by compressing it, but you can reduce the runout. And in reducing the runout, you will improve the performance of the grinding wheel. It may not be as good as a $5K or $10K or more commercial grinder, but it will be better than the uncompressed bearing. That's all I was saying. This is a "HOME" Shop Board after all.

Reading all the concerns about bearings above, I had another thought. This type of grinder, by definition, swings. Any slight angular error in the bore in the swing arm for the fit on the column will change the surface generated from a plane to a cone. This could easily be far, FAR greater than any slight tenths error generated by the wheel's bearings. Consider a six inch cup wheel - a common size. A 0.001" error from one side of the wheel to the other would be produced by an angular error in the arm's bore of InvTan(0.001/6) = 0.0095 degrees or 0.57 minutes. That's about 34 seconds or about the limit for my rotary table. Great care would be needed to insure the bore is even that good. For tenths accuracy, you would need to be about five times better in accuracy. I don't know if I can hold that kind of angular accuracy in my "home" shop. I would wonder about commercial shops. How would I/they even measure it?

Clearly, the pivot of the arm on the column is a very critical element. Far more critical than the motor bearings. And this error is not a random or periodic error that effects surface finish or areas of short dimensions, it is a non linear error over the totality of the surface being ground. It would produce a non flat surface the will rock if laid on a truely flat surface.

Perhaps this is one reason for the lack of popularity of this kind of grinder. Evan's concern with balance and massive parts is well founded.

I'm not saying it can't be done. I would personally want to include some kind of adjustment for the angle of the bore. A fine adjustment.

Evan
08-17-2008, 06:21 AM
Paul,

It's not so critical as what you think, The critical issue is that the motor shaft be aligned parallel with the swing axis in both X and Y. It would be much easier to include a three point adjustment for the motor mount than an adjustment of the column bearing. Even if the swing axis is tilted if the motor shaft is parallel to the swing axis the surface generated will be planar although it may be slightly tilted. That is of no concern since the grinder can grind it's own work surface.

lazlo
08-17-2008, 10:45 AM
First, I still stand by what I said above. I don't believe that you can correct all of the problems of a lesser bearing by compressing it, but you can reduce the runout.

Paul, compressing the bearing does absolute nothing to reduce the runout of the bearing. It reduces the internal clearance, that's all:

From the NTN Bearing Handbook:

Does internal clearance effect the bearing precision?
http://www.ntn.ca/faq.htm#clearprecision

Internal clearance is the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the NTN suffixes: C1, C2, C3, C4 and C5, where no suffix indicates normal clearance. C1 is a range less than C2. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4.

Precision is a range of tolerance on bearing dimensions. ISO and ABMA govern the precision ranges. ISO uses Class 0, Class 6, Class 5, Class 4, and Class 2 and ABMA uses ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively the systems are generally interchangeable. NTN uses P0 (usually not added to the part number), P6, P5, P4 and P2 to denote Class 0, Class 6, Class 5, Class 4 and Class 2, respectively.

Ultimately, clearance does not affect tolerance and tolerance does not affect clearance

Evan
08-17-2008, 11:02 AM
Paul, compressing the bearing does absolute nothing to reduce the runout of the bearing. It reduces the internal clearance, that's all:



Runout can be due to anything that allows the spindle to be off center. That includes clearance. Reducing clearance doesn't change bearing precision but it does reduce runout.

J Tiers
08-17-2008, 11:24 AM
I'm sorry for the distraction Oldtiffie but I won't stand for having my postings twisted and warped to mean something I didn't mean or say ( or write).

Actually, it appears you didn't write those exact words. Nonetheless, I for one certainly would have interpreted what you said, in context, as meaning approximately what is attributed, i.e. you can make the cheap bearings act like expensive ones by over-compressing them.

In any case, back in talking about the subject, instead of talking ABOUT talking..........

You DID ask a question :


Originally Posted by JTier
Truing CANNOT correct periodic errors with a repeating pattern frequency not equal to once-per rev. <end of quote from J Tiers>

<EVAN reply>That is true but only if it exists. Exactly where would periodic errors that are not directly related to revs come from in a direct drive system??? The fact that a bearing isn't precision doesn't mean it will always display such problems. I didn't say anything to the contrary either.


For your consideration, I give you the balls (or rollers). They turn, and they rotate en mass with the separator. The separator does not turn at the speed of either the race, it turns at a speed related to the ball diameter relative to the races.

In a lesser precision bearing, the balls are not sorted particularly for size. So as the separator rotates, different size balls come around, and the moving race shifts to allow them to pass. There is a separator frequency variation, and a ball pass frequency variation.

AS I ALREADY SAID, it isn't large, but it is another one of those things that separate a better ABEC class from a not as good class.

Those are not once-per rev errors. They cannot be compensated, and they will cause a rippled finish as the depth of cut varies.

If you use a swing type grinder, AS I SAID that effect is less, since only the camming action varies the depth of cut.



The latter will probably be quite noticeable when looking at a cheap bearing, especially a cheap bearing in a cheaply made product, like a cheap drill press, or a cheap grinder.<end of quote from J Tiers>
<Evan reply>All I said is that the finish is acceptable, as you can see in the photo it doesn't look like it was hacked with an axe nor does it have any patterns at all.


That is simply repeating what I said, quoting the WHOLE section, and not just the part which you wish to quibble with:



The latter will probably be quite noticeable when looking at a cheap bearing, especially a cheap bearing in a cheaply made product, like a cheap drill press, or a cheap grinder.

Noticeable when looking at a "grinder scale" of issues, which to me is stuff that goes from a couple thou down as far as you like.

Now, I want a grinder to deal with things of that scale, and make them go away..... smooth finish to settable and predictable tenths of tolerance. I strongly doubt that a DP or re-purposed cheap bench grinder will do that, except by chance.

However, if you want a ground finish to tolerances of 0.005 to a couple thou or so, there is no reason a cobbled-up grinding system cannot get to that area of tolerance, with a "ground finish".

Patterns are in the eye of the QC person.....

There certainly IS a pattern, but it may be one you can deal with. There is a pattern in the very best grinder's output.

If you like the result, please feel free to build whatever you want.

The problem comes when a person builds something which is "good enough for Bubba" and gives results "good enough for Bubba". Then if they proceed to try and show how its "just as good" as some fancy industrial tool that does that sort of job, there is a problem.

Not everyone will understand the limits, especially if the AUTHOR does not, and a reader may spend a lot of effort making the thing only to get the predictably mediocre results..

Or another problem is when an unsafe item, which they themselves can accept, is put forth as a great item for wide use.... One comes to mind...The EDM that was simply plugged stright into the wall, no isolation, no fuse, and IIRC, not even a power switch. It was actually printed in HSM, but drew a number of comments..... THAT sort of thing is no good either. HSM does not need a reduction in the number of readers of that sort.

The swing grinder article seems to combine BOTH sorts of problem.

The idea of a radial arm saw grinder is more the first type. There IS a risk of safety issues, however, and so there is an overlap. Incautious use might cause the wheel to bite in and be forced back to bash the user, run over their hand if placed badly, or break and throw wheel pieces. The user will necessarily be standing where stone fragments will hit. ( on a regular SG, you tend to be off to the side where the pieces would have to bounce at least once....... )

The chucked wheel in the drill press is BOTH problems... probable bad results, and a very good chance of breakage and possible injury because the one-bearing cheap DP suggested cannot stabilize the wheel at all, and probably will climb the work, dig in etc. The sideways force on the wheel will possibly cause breakage more easily than radial force. I would suggest using angle grinder wheels at least, and better not to do it at all.


Runout can be due to anything that allows the spindle to be off center. That includes clearance. Reducing clearance doesn't change bearing precision but it does reduce runout.

Preload is what takes care of clearance in angular contact bearings......... preload reduces the movement per unit force, which has a steep slope for an un-loaded bearing, and a much shallower slope for a loaded bearing. Preload simply does what it says.....pre-loads the bearing to take up initial clearance, etc.

wierdscience
08-17-2008, 11:25 AM
Paul, compressing the bearing does absolute nothing to reduce the runout of the bearing. It reduces the internal clearance, that's all:


Ultimately, clearance does not affect tolerance and tolerance does not affect clearance

Read further down-


Is it safe to use a C3 fit in place of a standard fit?

C3 is typically not referred to as a fit; it is the internal clearance in the bearing as defined above. A bearing fit is how tight or loose the shaft and housing hold the bearing in place.

When either of the rings of a bearing is tight fitted to its mating component (i.e. the shaft or housing), the resultant deformation of the ring causes a reduction in the amount of clearance in the bearing. A rotating bearing also produces heat due to material stress and through friction from rolling and sliding contact, lubricant shear, and seal contact. The bearing housing is usually stationary and is therefore better able to conduct heat away from the outer ring of the bearing. As a result, the temperature of the inner ring and rolling elements is usually 5 to 10 C higher than that of the outer ring. This results in greater thermal expansion of the inner ring and thus reduces the clearance in the bearing. If the shaft is being heated or if the housing is being cooled, the temperature difference will be even greater.

Selection of the proper initial bearing internal clearance must take all the foregoing factors into consideration. Assuming this has been done, it is never advisable to replace a bearing with one having a lower initial clearance. By the same argument, it is usually safe to substitute a larger clearance when the desired clearance is not available. (TOP)

What is preload?

Preload is an initial load or "negative clearance" given to a bearing before operation. This results in the rolling element and raceway surfaces being under constant elastic compressive forces at their contact points. This has the effect of making the bearing extremely rigid so that even when load is applied to the bearing, radial or axial shaft displacement does not occur."

If closing up the internal clearance and preloading the bearing achieves a more ridgid spindle,then by default it decreases the runout simply by the fact that the bearing has less internal clearence both radially and axially

Fact is there are about ten million mill drill,mini-mill,and 9x20 spindles out there that use common c3 ABEC3 bearings to good effect by simple press fit and preload

Paul Alciatore
08-17-2008, 11:28 AM
Evan,

Right you are. But any angular variance as the arm is swung would cause problems.

lazlo
08-17-2008, 11:31 AM
That's exactly right Wierd.

But you quoted two paragraphs from the NTN page with two totally different concepts: compressing the outer ring to reduce internal clearance (the first paragraph) and preloading the inner and outer rings (the second paragraph).

Pre-loading a bearing wedges the outer and inner rings together to take-up axial float. It's not related to compressing the outer ring to reduce the internal clearance of the balls, which has nothing to do with the run-out of the bearing.

This is the ABEC table of runout specs for precision angular contact bearings. Notice that internal clearance is never mentioned.
The critical factor in bearing runout is the inner ring and outer ring runout -- in other words, how true the inner and outer rings were ground at the factory, before the bearing was assembled.:

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABEC2.gif

lazlo
08-17-2008, 11:35 AM
Fact is there are about ten million mill drill,mini-mill,and 9x20 spindles out there that use common c3 ABEC3 bearings to good effect by simple press fit and preload

The mill drill,mini-mill,and 9x20 spindles use common, ungraded ball bearings -- they're not even ABEC-1, let alone ABEC-3. And again, you can buy ABEC-9 bearings with C3, C4 or even C5 internal clearance, since the internal clearance has nothing to do with the bearing runout.

That's the "ABEC Negative 5" expression that Evan used, and now wants to forget :)


Note that of course the spindle bearings are probably ABEC negative 5 or similar. It does an acceptable job for things like removing mill scale with minimum reduction in diameter and in particular the grinding of counterbores which saved the expense of the drill press the first time I used it.

But I agree, there's plenty of great work done with ungraded bearings. I just don't think you're going to have a lot of success using them in a Poor Man's Surface grinder, where the bearing runout is going to reflect directly in the surface finish.

wierdscience
08-17-2008, 12:44 PM
That's exactly right Wierd.

But you quoted two paragraphs from the NTN page with two totally different concepts: compressing the outer ring to reduce internal clearance (the first paragraph) and preloading the inner and outer rings (the second paragraph).

Pre-loading a bearing wedges the outer and inner rings together to take-up axial float. It's not related to compressing the outer ring to reduce the internal clearance of the balls, which has nothing to do with the run-out of the bearing.

This is the ABEC table of runout specs for precision angular contact bearings. Notice that internal clearance is never mentioned.
The critical factor in bearing runout is the inner ring and outer ring runout -- in other words, how true the inner and outer rings were ground at the factory, before the bearing was assembled.:

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABEC2.gif

You missed that I stated both radial and axial clearence

Of course internal clearence isn't mentioned in discussing angular contact bearings,there isn't any,nor can there be.

Runout is no indication of grind accuracy.To understand this you need to see how the bearings are made.Runout as stated in the chart is in the free state,not pressed in or crushed.

The races are rough machined out of bar stock or hot formed in a die.Then they are passes through an induction coil and dropped into a quench trough.This process leaves an egg shaped blank race due to the uneven cooling in the quench.

In grinding the OD is finished first,then the OD is grabbed in a collet to pull it round,finally the ID is ground and the rest of the process is finished.Both the OD and ID grinds are concentric,but the race isn't perfectly round hence the runout.

Angular contact mfg is very similar,but extra steps are taken such as normalising after heat treat to insure reduction of stress and a race that will stay round.Extra processing is used for sure such as higher polish and more precise ball grade selection.

The common grades of radial ball bearings are intended to be press fit on the OD and ID,the bore and shaft hold the races round.Angular contact do not use press fits as a norm,pressing would deform the races and negate the use in the firstplace.

Press fitting(crushing) the OD improves runout.A bearing that is crushed and not preloaded will have 3-6 points of contact between balls and races at any point in time as it revolves unloaded,the inner race and ball compliment simply ghost around in a circular orbit until acted upon by either a radial or axial load.At that point the shaft either centers as in the case of a vertical shaft or pulls to the loaded side in the case of radial loading.

Now if we preload the crushed bearing the contact point count will be equal to 2x's the ball compliment since everyone balls,races and cage are now singing and dancing in unison.

wierdscience
08-17-2008, 12:51 PM
That's exactly right Wierd.

But you quoted two paragraphs from the NTN page with two totally different concepts: compressing the outer ring to reduce internal clearance (the first paragraph) and preloading the inner and outer rings (the second paragraph).

Pre-loading a bearing wedges the outer and inner rings together to take-up axial float. It's not related to compressing the outer ring to reduce the internal clearance of the balls, which has nothing to do with the run-out of the bearing.

This is the ABEC table of runout specs for precision angular contact bearings. Notice that internal clearance is never mentioned.
The critical factor in bearing runout is the inner ring and outer ring runout -- in other words, how true the inner and outer rings were ground at the factory, before the bearing was assembled.:

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABEC2.gif

You missed that I stated both radial and axial clearence

Of course internal clearence isn't mentioned in discussing angular contact bearings,there isn't any,nor can there be.

Runout is no indication of grind accuracy.To understand this you need to see how the bearings are made.Runout as stated in the chart is in the free state,not pressed in or crushed.

The races are rough machined out of bar stock or hot formed in a die.Then they are passes through an induction coil and dropped into a quench trough.This process leaves an egg shaped blank race due to the uneven cooling in the quench.

In grinding the OD is finished first,then the OD is grabbed in a collet to pull it round,finally the ID is ground and the rest of the process is finished.Both the OD and ID grinds are concentric,but the race isn't perfectly round hence the runout.

Angular contact mfg is very similar,but extra steps are taken such as normalising after heat treat to insure reduction of stress and a race that will stay round.Extra processing is used for sure such as higher polish and more precise ball grade selection.

The common grades of radial ball bearings are intended to be press fit on the OD and ID,the bore and shaft hold the races round.Angular contact do not use press fits as a norm,pressing would deform the races and negate the use in the firstplace.

Press fitting(crushing) the OD improves runout.A bearing that is crushed and not preloaded will have 3-6 points of contact between balls and races at any point in time as it revolves unloaded,the inner race and ball compliment simply ghost around in a circular orbit until acted upon by either a radial or axial load.At that point the shaft either centers as in the case of a vertical shaft or pulls to the loaded side in the case of radial loading.

Now if we preload the crushed bearing the contact point count will be equal to 2x's the ball compliment since everyone balls,races and cage are now singing and dancing in unison.

Evan
08-17-2008, 01:17 PM
The mill drill,mini-mill,and 9x20 spindles use common, ungraded ball bearings -- they're not even ABEC-1, let alone ABEC-3. And again, you can buy ABEC-9 bearings with C3, C4 or even C5 internal clearance, since the internal clearance has nothing to do with the bearing runout.

That's the "ABEC Negative 5" expression that Evan used, and now wants to forget


Why should I forget it. I said it and I take ownership of it.

Now, about that ABEC-100 expression you say I like to use so much...

Did you forget about that?

The clearance affects runout at the spindle even when a bearing is preloaded. Preload doesn't alter the clearance in a bearing, it just makes the balls ride in a slightly different position in the race. They can still be shifted by working loads according to the clearance available and that produces runout. Compressing the bearing reduces that possibility and therefor reduces runout even under load.

note: I'm speaking of deep groove bearings, the sort fitted to most home shop machines.

lazlo
08-17-2008, 03:27 PM
This is the ABEC table of runout specs for precision angular contact bearings. Notice that internal clearance is never mentioned.
The critical factor in bearing runout is the inner ring and outer ring runout

Of course internal clearence isn't mentioned in discussing angular contact bearings,there isn't any,nor can there be.

That would be an interesting argument, except that those ABEC specifications apply to all ball bearings, including radial ball bearings. :) I have a pair of ABEC-5 radial ball bearing sitting on my desk. The same runout specs apply.


Runout is no indication of grind accuracy.

Runout is determined by the grind accuracy of the inner and outer races.

From "Bearing Design in Machinery"
http://books.google.com/books?id=1l1-mW27G5wC&pg=PA412&lpg=PA412
http://bks1.books.google.com/books?id=1l1-mW27G5wC&printsec=frontcover&img=1&zoom=1&sig=ACfU3U14_1df1o-5_MjdoOhubBnXFMRJNw

Bearings of ABEC 7 and 9 precision are for ultraprecision applications. The American Bearing Manufactures Associateion (AMBA) has adopted this standard for bearing tolerances, ANSI/ABMA-20, 1996, which is accepted as the international standard.

The most important characteristics of precise bearings are the inner ring and outer rings run-outs. However, tolerances of all dimensions are more precise, such as inside and outside diameters, and width.



Press fitting(crushing) the OD improves runout.

Take a ring -- say a wedding band. Crush it uniformly with a strap wrench. What happens? It deforms. Which is why the NTN bearing handbook warns not to install a bearing in a tighter fit than is recommended in the bearing design handbook.

Or put more simply: do you think that machine designers, after all these years, have missed such a trivial improvement, that jamming a bearing in a hole tighter than it was designed for is going to improve it's runout? Does jamming an ABEC-3 bearing into a tight hole turn it into an ABEC-5? Does jaming an ABEC-7 bearing into a tight hole turn it into an ABEC-9? What's that make an ABEC-9 in a tight hole -- an ABEC-11? :D

lazlo
08-17-2008, 03:43 PM
That would be an interesting argument, except that those ABEC specifications apply to all ball bearings, including radial ball bearings. :) I have a pair of ABEC-5 radial ball bearings sitting on my desk. The same runout specs apply.

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABEC56206.gif

J Tiers
08-17-2008, 04:04 PM
The clearance affects runout at the spindle even when a bearing is preloaded. Preload doesn't alter the clearance in a bearing, it just makes the balls ride in a slightly different position in the race. They can still be shifted by working loads according to the clearance available and that produces runout. Compressing the bearing reduces that possibility and therefor reduces runout even under load.

note: I'm speaking of deep groove bearings, the sort fitted to most home shop machines.

Suggest you learn about bearings. Look at a curve of deflection vs load for any bearing, presumably ANGULAR CONTACT, which are the bearings most commonly fitted for any precision spindle application, as for GRINDERS etc.

What do you see?

You see that the preload reduces the deflection vs load. A certain amount of preload will enter the straight-line part of the curve. Almost ANY will get you out of the initial steep portion.

Your statement evidently pooh-poohs preload and attempts to imply that the preload has little effect on deflection and that clearance has far more, with or without preload....

I think you will find that is not true with angular contact bearings, which are the ones "fitted to most home shop machines" (such as Bridgeport, Logan, Sandford, and even Atlas, if you count tapered roller bearings as "angular contact", which you would have to ).

If you are talking about cheap chinese machines made for the bottom feeders, who KNOWS what they have in them?

Even with deep groove ball bearings, Dumore, for instance used deep groove with a preload to take up the clearance.

Evan
08-17-2008, 06:20 PM
Suggest you learn about bearings. Look at a curve of deflection vs load for any bearing, presumably ANGULAR CONTACT, which are the bearings most commonly fitted for any precision spindle application, as for GRINDERS etc.



I suggest you learn to read. I specifically excluded angular contact as deep groove bearings are the most commonly fitted on home shop machines. The rest of your post does not apply to my statement.


I think you will find that is not true with angular contact bearings, which are the ones "fitted to most home shop machines" (such as Bridgeport, Logan, Sandford, and even Atlas, if you count tapered roller bearings as "angular contact", which you would have to ).


Unfortunately, those aren't the most common home shop machines. If you are talking about American made machines then South Bend is the most common lathe. It doesn't have rolling element bearings. As for tapered rollers, I already suggested them a long while earlier.

As for the most common machines overall, that would be Chinese by now. They usually have deep groove bearings.

oldtiffie
08-17-2008, 06:37 PM
In this thread - the OP title of which is still "Poor man's Surface Grinder" - I would think that the "poor" man may have got lucky if he were illiterate and could not read all this stuff which is pretty irrelevant to a "poor man's surface grinder" (and) if he just got on and made one from the junk box in his shop.

Even if he were were very literate - which I think he was/is - he'd have been more than intelligent enough to ignore all this and "get on with it" anyhow.

I suspect that he has out-paced just about everyone and eventually made a successful "poor man's surface grinder" using his own resources.

wierdscience
08-17-2008, 07:09 PM
That would be an interesting argument, except that those ABEC specifications apply to all ball bearings, including radial ball bearings. :) I have a pair of ABEC-5 radial ball bearing sitting on my desk. The same runout specs apply.



Runout is determined by the grind accuracy of the inner and outer races.

From "Bearing Design in Machinery"
http://books.google.com/books?id=1l1-mW27G5wC&pg=PA412&lpg=PA412
http://bks1.books.google.com/books?id=1l1-mW27G5wC&printsec=frontcover&img=1&zoom=1&sig=ACfU3U14_1df1o-5_MjdoOhubBnXFMRJNw

Bearings of ABEC 7 and 9 precision are for ultraprecision applications. The American Bearing Manufactures Associateion (AMBA) has adopted this standard for bearing tolerances, ANSI/ABMA-20, 1996, which is accepted as the international standard.

The most important characteristics of precise bearings are the inner ring and outer rings run-outs. However, tolerances of all dimensions are more precise, such as inside and outside diameters, and width.




Take a ring -- say a wedding band. Crush it uniformly with a strap wrench. What happens? It deforms. Which is why the NTN bearing handbook warns not to install a bearing in a tighter fit than is recommended in the bearing design handbook.

Or put more simply: do you think that machine designers, after all these years, have missed such a trivial improvement, that jamming a bearing in a hole tighter than it was designed for is going to improve it's runout? Does jamming an ABEC-3 bearing into a tight hole turn it into an ABEC-5? Does jaming an ABEC-7 bearing into a tight hole turn it into an ABEC-9? What's that make an ABEC-9 in a tight hole -- an ABEC-11? :D

Your are missing the point entirely and confusing terms.The ABEC specs are grind accuracy with the bearing in the free state NOT FITTED INTO ANYTHING.Until a bearing is mounted it is egg shaped even a ABEC-9,the only difference between the grades is how much eggshape and the finish quality.That's why the ABEC 9 have high point marks on the races.If you don't believe me grab a few ABEC 1's and mic the OD's.They will be within .0002" of round,some may even be perfect.but most will be egg shaped by that amount.If you have some,then check some ABEC 9's,they should be within .000019" oh,that's right,it's a HS and you might not have equipment capable of measuring below .0001":D

Will pressing an ABEC-1 bearing into a hole improve finish quality or ball grade selection?No,but it will improve TIR simply be correcting eggshape.

If you COMBINE that with preload then the lower grade bearing will be perfectly capable of sufficent accuracy for the HSM surface grinder.

What manufactures do is tailor the design to the bearings they decide to use.

Why slip fit an ABEC 3 cO bearing into a housing and have to retain it with a snap ring,when you can press fit an ABEC1 c3 into the same housing and achieve the same performance without the snap ring and required machining?

Or the other way round,why machine a press fit for a ABEC 3 c3 when an ABEC 5 cO retained with Loctite will achieve the same result?

Since preload removes float both radially and axially and crush removes internal clearance it will yeild a bearing that will work quite well for a shop built swing grinder especially since end float is what is needed to be removed.

Personally I wouldn't use balls since tapered roller bearings are so much easier and cheaper,but to each his own.

lazlo
08-17-2008, 08:20 PM
Your are missing the point entirely and confusing terms.The ABEC specs are grind accuracy with the bearing in the free state NOT FITTED INTO ANYTHING.

Right, the ABEC tables are the accuracy specs of a radial or angular contact bearing before it's installed.


Until a bearing is mounted it is egg shaped even a ABEC-9,the only difference between the grades is how much eggshape and the finish quality.That's why the ABEC 9 have high point marks on the races.

They're not egg-shaped, they're whatever shape the grinder used to grind them, as long as the maximum runout meetings the ABEC rating. Most bearing races are ground on a cylindrical grinder, so they're actually tri-lobed, but that makes no difference, since they still meet the ABEC spec for which they're designed.


That's why the ABEC 9 have high point marks on the races.

All precision bearings, from ABEC-5 through ABEC-9 have both the inner and outer races marked. But they're not marked because they're egg-shaped: both the inner and outer races are marked with the point of maximum runout. This is so you can install the bearing so both the inner and outer points of maximum runout are opposite the spindle's point of maximum runout.

If you don't mark the spindle when you remove the old bearings, you'll get bad runout, even with precision bearings, because the two points of maximum runout are not subtracting out.



Will pressing an ABEC-1 bearing into a hole improve finish quality or ball grade selection?No,but it will improve TIR simply be correcting eggshape.

That's wrong for a very simple reason: the ABEC ratings specify the inner and outer ring runout out of the box. When you install the bearing, the completed spindle assembly always has more runout than the bearing before it was installed. If installing the bearing was somehow correcting for a flawed geometry, the bearing runout would be even better when installed, which just doesn't happen.

To put that in perspective, the max radial runout of the ABEC-7 bearings in a Bridgeport spindle are 50 millionths of an inch. When installed, the best Bridgeport spindles with have around 5 times that much runout (around 2 1/2 tenths).

That's why high-end machinery install the bearings, and then grinds the spindle in the bearings, to minimize overall runout.

wierdscience
08-17-2008, 09:17 PM
Okay,my 20 year+ experience gives in to the book you read and there simply is no way to make a decent spindle with less than ABEC9 bearings.Just don't tell Bridgeport.

Evan
08-17-2008, 09:33 PM
That's wrong for a very simple reason: the ABEC ratings specify the inner and outer ring runout out of the box. When you install the bearing, the completed spindle assembly always has more runout than the bearing before it was installed. If installing the bearing was somehow correcting for a flawed geometry, the bearing runout would be even better when installed, which just doesn't happen.


[Shakes head] Of course it doesn't happen. You then have other factors to measure. In order to actually see the difference caused to the bearing by installing the bearing the rest of the spindle assembly would have to be perfect. Now that just doesn't happen. It does not mean properly installing the bearing makes it somehow worse which is what you are implying. If that were really the case it would be mentioned in every book that deals with precision machine maintenance. It isn't. Of course the bearing ratings are for an uninstalled bearing. No other way of specifying the ratings is possible.

Once you install the bearing it is in a unique condition that is specific to the machine it is in. There is no way of specifying the bearing parameters for that in advance. It remains however that bearing crush A: is Real and B: reduces internal clearance.

All constraining mechanisms, which includes bearings, limit one or more of the six possible degrees of freedom of an object free in space. They are X,Y and Z roll and x, y and z translation. A bearing contrains a shaft in five degrees of freedom leaving just one, roll in Z. However, one must not overconstrain. That is why bearings have clearance. An overconstrained system is impossible to build reliably and is prone to failure and poor operation. Constraint systems must allow for error motions and in a spindle one of those is total runout of the assembly. That accounts for two degrees of freedom, translation in X and Y. It can also involve a slight degree of roll in those axes as well.

Reducing internal clearance reduces at minimum four degrees of freedom out of six possible, radial translation in X and Y and to a lesser extent roll and possibly axial translation.

lazlo
08-17-2008, 09:53 PM
Okay,my 20 year+ experience gives in to the book you read and there simply is no way to make a decent spindle with less than ABEC9 bearings.Just don't tell Bridgeport.

Huh? How do you read that out of my response? My point is that there's no bearing book or bearing engineer/machine designer on earth that says that the accuracy of the bearing improves when it's installed.

Bridgeport's (and most other modern machine tools) get along just fine with the ABEC-7 bearings they're shipped with, because 2 1/2 tenths runout is fine for the vast majority of commerical apps.

This whole conversation started because Evan claimed that you could improve the runout of a cheap bearing by overcompressing it, which is just wishful thinking.

If you need a certain degree of accuracy, whether on your Bridgeport spindle or your Poor Man's Surface Grinder, then pay for it. But don't expect precision bearing performance with cheap bearings.

lazlo
08-17-2008, 09:55 PM
Reducing internal clearance reduces at minimum four degrees of freedom out of six possible, radial translation in X and Y and to a lesser extent roll and possibly axial translation.

From the NTN Bearing Handbook:

Does internal clearance effect the bearing precision?
http://www.ntn.ca/faq.htm#clearprecision

Internal clearance is the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the NTN suffixes: C1, C2, C3, C4 and C5, where no suffix indicates normal clearance. C1 is a range less than C2. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4.

Precision is a range of tolerance on bearing dimensions. ISO and ABMA govern the precision ranges. ISO uses Class 0, Class 6, Class 5, Class 4, and Class 2 and ABMA uses ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively the systems are generally interchangeable. NTN uses P0 (usually not added to the part number), P6, P5, P4 and P2 to denote Class 0, Class 6, Class 5, Class 4 and Class 2, respectively.

Ultimately, clearance does not affect tolerance and tolerance does not affect clearance

..and here is their definition of the ABEC tolerances. The yellow dial is representative of a Dial Indicator used to measure the runout:

http://i164.photobucket.com/albums/u15/rtgeorge_album/ABECTolerances.gif

Evan
08-17-2008, 09:58 PM
That's nice. Clearance does affect runout when installed which they aren't talking about.

lazlo
08-17-2008, 10:04 PM
That's wishful thinking Evan.

I've given examples from several major bearing design handbooks explaining that internal clearance has nothing to do with bearing runout.

So show me a single reference that corroborates your claim that jamming a bearing into an undersized hole will improve it's runout.

lazlo
08-17-2008, 10:14 PM
From ESL Bearing:
http://www.eslbearing.com/faq.htm#What%20is%20the%20difference%20between%20A BEC%203%20and%20C3?%20Does%20the%20fit%20get%20bet ter%20going%20up%20to%20C4%20or%20down%20to%20C2?

What is the difference between ABEC 3 and C3? Does the fit get better going up to C4 or down to C2?

ABEC 3 is an AMBA tolerance class. C3 is an internal clearance specification. Fit is the relationship between the bearing bore and outside diameters to the housing bore and shaft outside diameter. Tolerance, clearance and fit are independent dimensions, although in some cases choosing a larger internal clearance can allow you to use a tighter interference fit.

oldtiffie
08-17-2008, 10:38 PM
All of this "hi-end" stuff it all very interesting - truly - but I am damned if I can see what the relevance of it all is to an "el cheapo" functional surface grinder.

This has morphed into another "BP spindle cartridge" effort.

Some of the bearings alone being kicked around here are more than a reasonable basic REAL surface grinder can be bought for on eBay, Craig's List or at a local dealer.

Making or reconditioning such a spindle cartridge will probably well beyond many in this forum as well.

All that was asked for was in dp's (Dennis's) OP was:


Anyone tried using a modified radial arm saw for a surface grinder? Something needs to be done to keep the dust out of the motor, but for clean up work it seems like it might be feasible, and in the realm of home shop machinery solutions. I'm curious because I just picked up an older Delta Super 900 saw in utterly excellent shape for $40.00. An example is shown here: http://www.owwm.com/photoindex/detail.aspx?id=3825

What a great site that is for older woodworking machine information!

So let's get back to basics - what is "cheap" and functional.

So let's see what the OP was talking about:

The "Delta Super 900" saw is shown at:
http://www.owwm.com/photoindex/detail.aspx?id=1657

other references are at:
http://www.google.com.au/search?hl=en&q=%22Delta+Super+900%22&btnG=Search&meta=

So how about we address that instead of flying off at tangents (or OT hi-jacks).

I would guess that many of the basics of a reasonable but not necessarily "dead nuts" or "Tool room" machine or quality are there - in the OP's saw - but with a bit more focused attention it may well be able to be modified to suit and make a cheap, serviceable surface grinder.

Perhaps the lateral motions could incorporate cheap linear rails - not too much different to many mitre saws.

So, let's keep it simple, cheap, creative, quick and functional.

I would bet that there are a lot more people here who will be lots more interested in a cheap surface grinder than they are in "hi-brow" and "way out there" discussions on super accurate, super-performing, super-expensive, difficult to make grinder spindle assemblies - which is only as far as this current discussion on the merits or otherwise of super-expensive bearings has taken us.

wierdscience
08-17-2008, 10:45 PM
Okay simple example-

Imagine a typical ball bearing,pick out any three ajacent balls.Turn the race so that the center ball is at top dead center.Mount an indicator at TDC.

Now turn the race so that two adjacent balls are at 10:00 and 2:00

Will a bearing with no clearance have more or less runout than one with clearance?

lazlo
08-17-2008, 10:46 PM
Preload doesn't alter the clearance in a bearing, it just makes the balls ride in a slightly different position in the race.

Preload, by definition, removes the internal clearance by wedging the inner and outer races. That applies to radial or angular contact bearings.

Preloads
http://www.rotoprecision.ca/Products/Miniature_Bearings/Internal_Geometry.html

Preloading is used to remove the internal clearance of a bearing and is achieved by applying a permanent thrust load in an axial direction. Preloading is used to eliminate radial and axial play, increase system rigidity, reduce run out, increase the assembly’s tolerance for vibration, and reduce operating noise.

Evan
08-17-2008, 11:20 PM
That's wishful thinking Evan.

I've given examples from several major bearing design handbooks explaining that internal clearance has nothing to do with bearing runout.

So show me a single reference that corroborates your claim that jamming a bearing into an undersized hole will improve it's runout.


I'll make it very simple. Loose= more runout. Tight=less runout

You have a problem of your own making, probably intentional. You are choosing to define runout (without telling anybody) as the variation of the thickness of the walls of the bearing races.

I, on the other hand am using the well accepted definition that is the description of the path the center of the spindle takes as it rotates when supported by that bearing. That is what the majority of the people reading this also think (I am quite sure) since that is the runout we are all concerned with. All you are accomplishing is to appear ignorant and obstinate.

You know perfectly well that a spindle that is mounted in a bearing with x clearance will exhibit greater runout than a spindle in a bearing with x-1 clearance. So does everyone else that is still reading this.

I will repeat, I am referring to deep groove ball bearings, not angular contact bearings.


Preload, by definition, removes the internal clearance by wedging the inner and outer races. That applies to radial or angular contact bearings.


That's right. Since nothing is infinitely rigid the preload is like a spring and the clearance the bearing has in the unloaded condition is the room that spring has to move in when acted on by working loads. Reduce that space in the first place and reduce the runout under load.

lazlo
08-17-2008, 11:32 PM
Preload doesn't alter the clearance in a bearing


Preload, by definition, removes the internal clearance by wedging the inner and outer races. That applies to radial or angular contact bearings.


That's right.

Uhhhh???? :D

J Tiers
08-17-2008, 11:34 PM
I suggest you learn to read. I specifically excluded angular contact as deep groove bearings are the most commonly fitted on home shop machines. The rest of your post does not apply to my statement.


Unfortunately, those aren't the most common home shop machines. If you are talking about American made machines then South Bend is the most common lathe. It doesn't have rolling element bearings. As for tapered rollers, I already suggested them a long while earlier.


Ixnay...... I mentioned deep groove also..... and mentioned taperd as another "angular contact" type. No need to be a "ball bearing bigot".

And the effect is still there, it just is a fact that deep groove bearings are not designed from the git-go specifically for preload. Angular contact ARE.

I have not seen any curves for those, but they are not that different in shape of the races, and should have the same 'wedging" action as a purpose-made angular contact.




As for the most common machines overall, that would be Chinese by now. They usually have deep groove bearings.

So you are saying chinese lathes and bridgeport clones have deep groove ball bearing spindles? Hmmmm I see roller bearings mentioned for them...... obviously you mean the cheaper stuff..... and probably not lathes.

In fact you likely mean a subset of chinese machines use deep groove.

If the lathes had those, I expect they would chatter like a forest of monkeys.... but even the chinese machines are generally usable to that degree, and don't chatter from that cause.

Now if you mean drill presses etc, sure. They probably DO have deep groove, at least we HOPE they are really the deep groove type.... :eek: Maybe even some cheap mill-drills do as well.

For sure any bench grinder does........

Of course they can be preloaded, and the preload will have the effect of reducing deflection, and absolutely eliminating clearance-related unloaded runout. Has to, it eliminates clearance, that is the whole point.

On an angular contact bearing, the preload moves the balls to the correct position.

On a deep groove, it moves the balls toward one side of the race. But since preload is less than the maximum allowable force, it cannot force the balls off the ground path, etc. It just "wedges" them in much the manner of the angular contact.

I have more than one machine that uses preload to eliminate clearance, and clearance-related problems, in deep groove bearings.

Yes, it works. Yes, it eliminates the clearance problem, and does away with the deflections due to clearance.

No, there may NOT be the sort of graphed data on preload vs deflection that is given for angular contact. But that does NOT show it won't work, it just shows that the manufacturers assume one with that sort of problem will naturally use the proper bearings to deal with it. And that the preload is not used optimally in a deep groove vs an angular contact type.

lazlo
08-17-2008, 11:40 PM
I'll make it very simple. Loose= more runout. Tight=less runout

Nice simplification, but unfortunately it's untrue. Which is why every bearing handbook on earth, including the three that I've posted already, say that the internal clearance of the bearing has nothing to do with the runout of the bearing.

The runout of the bearing is determined almost entirely by how accurately the inner and outer races are ground.

From "Bearing Design in Machinery"
http://books.google.com/books?id=1l1...A412&lpg=PA412

Bearings of ABEC 7 and 9 precision are for ultraprecision applications. The American Bearing Manufactures Associateion (AMBA) has adopted this standard for bearing tolerances, ANSI/ABMA-20, 1996, which is accepted as the international standard.

The most important characteristics of precise bearings are the inner ring and outer rings run-outs. However, tolerances of all dimensions are more precise, such as inside and outside diameters, and width.


You know perfectly well that a spindle that is mounted in a bearing with x clearance will exhibit greater runout than a spindle in a bearing with x-1 clearance.

It doesn't Evan. Internal clearance is all about thermal management. You need enough internal clearance to allow for the balls to expand while the spindle is rotating. So higher RPM requires higher internal clearance.

Look at any precision bearing catalog: you can buy the same ABEC-7 bearing in C2, C3, or C4 internal clearance. All three bearings have exactly the same runout.

Evan
08-17-2008, 11:49 PM
Of course they can be preloaded, and the preload will have the effect of reducing deflection, and absolutely eliminating clearance-related unloaded runout. Has to, it eliminates clearance, that is the whole point.


It cannot remove the clearance the bearing has when unloaded. That space is still there under preload and the components of the bearing are still able to move within that space when loads are applied. If that space is reduced the the room to move is reduced. You can absolutely remove clearance related unloaded runout and that is very useful if all you want to do is watch the spindle turn. The moment you start actually using the machine the clearance matters, preload or not.

An interesting point is maded in the article in the thread I posted on chatter problems. It turns out that star pattern chatter when drilling is caused by the drill bit winding up and becoming shorter, then unwinding and becoming longer. It's hard to imagine a 1 1/2 inch drill bit doing that but it does. Likewise, a spindle stretches and bends as working loads are applied. Those are the error motions I earlier mentioned that occur in the constrained axes. They cannot be eliminated, only accomodated.

lazlo
08-17-2008, 11:50 PM
As for the most common machines overall, that would be Chinese by now. They usually have deep groove bearings.

So you are saying chinese lathes and bridgeport clones have deep groove ball bearing spindles? Hmmmm I see roller bearings mentioned for them...... obviously you mean the cheaper stuff..... and probably not lathes.

In fact you likely mean a subset of chinese machines use deep groove.

If the lathes had those, I expect they would chatter like a forest of monkeys...

Jerry's right -- the 7x10, 9x20,... lathes and the Mill/Drills use tapered roller bearings. The Bridgeport clones all use angular contact bearings.

The only Chinese machines I can think of that use radial bearings in the spindle are the drill presses.

Evan
08-17-2008, 11:59 PM
It doesn't Evan. Internal clearance is all about thermal management. You need enough internal clearance to allow for the balls to expand while the spindle is rotating. So higher RPM requires higher internal clearance.



The majority of machining is not done at maximum rpm. At normal machining rpm what I said holds true and that is what matters most of the time.


The only Chinese machines I can think of that use radial bearings in the spindle are the drill presses.

All of the mini mills use deep groove ball bearings.

J Tiers
08-18-2008, 12:28 AM
It cannot remove the clearance the bearing has when unloaded. That space is still there under preload and the components of the bearing are still able to move within that space when loads are applied. If that space is reduced the the room to move is reduced. You can absolutely remove clearance related unloaded runout and that is very useful if all you want to do is watch the spindle turn. The moment you start actually using the machine the clearance matters, preload or not.


Sigh............

The geometry is somewhat similar between a radial (half the race) and an angular contact....

The point of preload is to ELIMINATE the clearance by forcing the balls to run in a different area of the race, one where the clearance is not present..... This is really true of BOTH types, although the angular contact REQUIRE preload.

This is done by an axial force applied..... In most machines this is a tension in the spindle.......

The balls ride up a relatively shallow slope of the race to the new position.......

To force them back to the "looser" position, requires a side force several times larger than the axial preload, due to the slope.

it isn't a case of simply overcoming a light preload in a 1:1 manner, and then being back where you were...... if that was the case, preload would be of no practical use....

A bearing with a capacity of 1000 lb axial force, might have a preload of 50 or more lb applied. If the slope is such that it takes 10x the side force to overcome axial force, it will take 500lb to zero the axial preload. But, note, that is not actually MOVING the spindle yet, it is just overcoming the preload so that you CAN move it. You STILL have the springiness of the spindle in tension to overcome to actually displace the balls.

Now, it may not be POSSIBLE to apply 500lb force via the cutter, or the wheel..... certainly it may not be ADVISABLE.

If you cram in the grinding wheel to the work under 500lb pressure you probably deserve what you get......

For any machine with a decent design, the bearing capacity, and preload are designed to stand up to the allowable side loads.

if you are rolling your own, you may need to do some design work to ensure that the matters are properly taken care of.

But the preload most certainly can and does stand up to "enough" side load without reverting to the unladed condition and clearances. The geometry of the races ensures that.

It is NOT a simple matter of applying a small side load and erasing the effects of preload, despite the airy "if you <do thus and so>........" statements of Evan.

What Evan says, would, if true, mean that preload was almost totally useless, for deep groove as well as angular contact.

Evan
08-18-2008, 12:43 AM
A bearing with a capacity of 1000 lb axial force, might have a preload of 50 or more lb applied. If the slope is such that it takes 10x the side force to overcome axial force, it will take 500lb to zero the axial preload. But, note, that is not actually MOVING the spindle yet, it is just overcoming the preload so that you CAN move it. You STILL have the springiness of the spindle in tension to overcome to actually displace the balls.


Incorrect. I'll make a drawing to show why.

Evan
08-18-2008, 02:35 AM
No matter how little side load is placed on the preloaded spindle it will deflect in proportion to that side load. There is no "overcoming" of the preload that must happen first. The preload simply makes the system stiffer and increases the amount of sideload required to produce a given deflection but deflection occurs no matter what the side load or preload.

The effectiveness of the preload varies depending on the preloaded clearance, especially with deep groove bearings of the type used in all mini mills and lathes. Bearing crush will reduce the available preloaded clearance which changes the geometry in a manner that increases the effectiveness of the preload and makes the system stiffer.

This illustration shows why.

http://vts.bc.ca/pics5/bearingcrush.jpg


This is the bearing type used in the mini mills and lathes.

http://vts.bc.ca/pics5/bearing.jpg

radish1us
08-18-2008, 02:36 AM
Can't you clowns just give up, then agree, to disagree.

oldtiffie
08-18-2008, 05:17 AM
Thanks radish1us.

I suspect that they are concerned with putting on a spectacle/spectacular for what they possibly consider to be the edification of the proletariat, the "hoi polloi" and the "great unwashed" while just slamming and slagging each other.

http://en.wikipedia.org/wiki/Proletariat

http://en.wikipedia.org/wiki/Hoi_polloi

http://en.wikipedia.org/wiki/The_Great_Unwashed

It is more than a little self-indulgent as well.

I am sure that they are providing quite a spectacle for the rest of us - but I'm equally sure that its anything but the spectacle in our - or more particularly - my, eyes than that they intended.

I am quite sure that if I wanted or needed this sort of discussion or detail, a dedicated thread would suffice.

Futher I am reasonably sure that I, as would many others, be quite able get and interpret such data, instructions and technical assistance as I required for myself.

Now, can we get back to seeing if we can develop a range of viable options for a "poor mans' surface grinder" as I am sure that will be of more interest to many and particularly those of us who want to see how to get or make such a grinder.

To do otherwise is at best bordering on gross bad manners, selfishness and plain ignorance.

I do think the OP is owed an apology at least.

Evan
08-18-2008, 06:17 AM
You needn't read it. I don't read a majority of the threads on the BBS. Think of all the time I save. Methinks tiffie, you love to hate this sort of discussion.

oldtiffie
08-18-2008, 07:10 AM
Methinks tiffie, you love to hate this sort of discussion.

Evan, you can think what you damn well like.

You have it 100% wrong.

I like those sorts of discussions - in their place - preferably on a dedicated thread - and not when they constitute a "hi-jack" and OT for the use and purpose of a (select/"elitist") few to the exclusion of many others and any or much or most of the base/original intent of the OP.

J Tiers
08-18-2008, 08:17 AM
Thanks radish1us.

I suspect that they are concerned with putting on a spectacle/spectacular for what they possibly consider to be the edification of the proletariat, the "hoi polloi" and the "great unwashed" while just slamming and slagging each other.

To do otherwise is at best bordering on gross bad manners, selfishness and plain ignorance.

I do think the OP is owed an apology at least.

Bless you with a brick...... twice.

I am not apologizing.... I keep dragging this back on topic by relating the discussion to the cobbed-up saw (and swing) grinders that are the original issue.

it keeps being dragged off into minutia.

Elitist? bag that...... I don't care if someone else wants in also...... the more the merrier. No elitism here, except in YOUR mind.

I'm actually getting tired of intransigent insistence on goofy wrong ideas, and am about ready to let a certain person be "right" as usual.

For another thing, the original question seems answered anyhow...... You CAN use a saw as a grinder, if you are not particular about anything but a "ground" finish, and don't need to be able to predictably dust off a tenth or two.

And if you are not overly concerned about possibly cracking a wheel that is directly in-line with your head or other parts of you.

Seems pretty well put to bed.............

And in any case, the whole reason for the bearing discussion is that the bearings are what makes a lot of the difference between a decent grinder and what you get from using a saw or drill press as an improvised grinder. That and solidity of basic construction. If construction is a given (big if) the bearings are what is left.

So it actually is On-Topic.

If this was an email group I could understand the Tiff getting upset about clogging his inbox. But it's not. If if he looks at the thread, he gets what he deserves.

Tiffie, you are NOT the moderator here, and what you think does not constitute a law. Sorry if this is news, but it has to be said.

As far as slamming and slagging. I don't believe anyone in this discussion has acted like some others on the board by actually resorting to calling people obscene names. Tiffie has not, but some others have..............


Evan:
If any hearing actually looked like your pictures, with that sort of proportional clearance, the blinking thing would be scrap.............

Evan
08-18-2008, 09:00 AM
If any hearing actually looked like your pictures, with that sort of proportional clearance, the blinking thing would be scrap.............

Right. The proportions are exaggerated for the purpose of explanation. Standard practice.

oldtiffie
08-18-2008, 09:18 AM
I have no problems with your post JT.



.................................................. ..
..................................................

And in any case, the whole reason for the bearing discussion is that the bearings are what makes a lot of the difference between a decent grinder and what you get from using a saw or drill press as an improvised grinder. That and solidity of basic construction. If construction is a given (big if) the bearings are what is left.

Yep - agreed. It is the total package that counts - construction generally and bearings too.

"Cheap and effective" seem to be the main criteria here although the definition of each will be specificc to each individual/owner.

A lot of creative and lateral thinking applied within generally available resources in an average HSM shop would need to to be considered as well.

I have no problem with bearings, provided they are cost-effective and can be fitted relatively easily into the existing motor end-caps and the motor rotor/spindle. The quality - or lack of it - as regards the adequacy of the stator pockets and rotor journals might well be questionable and will or may at least partially negate the use of expensive bearings.

The discussion thus far on the very precise bearings seem to have settled or only considered the spindle in isolation from that on the rotor which may not necessarily be very well dynamically balanced at all. The orientation of the spindle is important - particularly as to whether the bearings are going to have to support the lateral weight/thrust of the mass of the motor if mounted vertically or whether the motor/spindle is mounted horizontally. Again, there is no mention of the speed of the rotor/spindle. If the existing saw motor assembly is used, manufacture of a "difficult-to-make" spindle assembly may not be a consideration.

If these concerns can be addressed and resolved, there is a good case for proceeding further towards completion by considering the uses of linear slides for "X" and "Y". Lead-screws may not be needed for "X" as "hand-operated" "linkages" may suffice. A lead-screw may not be needed for "Y" either but that is for the owner/user to decide.

The existing yoke/support system for the proposed saw may be used to turn the "grinding wheel" assembly to the "longitudinal ripping" position (at 90 degrees to the over-head ways). A more conventional "surface grinder" configuration may well be achieved. This will be a sort of "bridge" or "gantry" configuration. It should include the "fine-feed" screw-driven very good "down-up" feed mechanism/s.

In regard to the saw in the OP, I'd have at least considered supporting the "out-board" (front) cantilevered end of the main traverse way to convert it to a end-supported beam sufficiently "stiff" so as to form a partial "portal frame" structure. The quality of the "ways" and the stability of the motor and support frame/structure could do with some thought as well.

The size of the grinding wheel will be dictated by the size of the motor stator/housing for optimum use and clearance. I have the same limitation on my T&C grinder when I use it as a surface grinder. I use 7" wheels but the motor housing is 6", so once the wheels are 6" they can only be used for surface grinding where the body of the motor does not have to pass over anything in its path on the grinder table. Other than that, it is fine.


If this was an email group I could understand the Tiff getting upset about clogging his inbox. But if he looks at it, he gets what he deserves.

True and true. If I stick my neck out and "ask for it" and "get it" I have no complaints as it is my own fault. I just try to "grin and bear it" and "take my medicine". I will respond if and as I think necessary at the time.


Tiffie, you are NOT the moderator here, and what you think does not constitute a law. Sorry if this is news, but it has to be said.
I never thought nor said I was the Moderator - and I sure don't want or need to be. So I don't make, interpret or enforce the law - that's for VP/George Bullis to do as he thinks fit.

Its not news - new or old - to me - and I guess to anyone and everyone else.

I do like to see a thread generally keep on topic as per the OP as it only makes much it that much harder than it needs be for those that use the "search" facility. It can make a mockery of the oft-recited advice to "use the search".

I have only got the rights of anyone and everyone else - as we are all equals here.


As far as slamming and slagging. I don't believe anyone in this discussion has acted like some others on the board by actually resorting to calling people obscene names. Tiffie has not, but some others have..............

I sure have done my bit (and then some?) of ill-advised comment and distractions - which I often regret in retrospect - but try as I might I can't see it changing much.

Thanks for the "pull-back" to topic.

I just hope it can be discussed and developed further for a range of options that might be useful for those that might be considering making, adapting or even buying ("the makings of"??) a cheap "Poor man's Surface grinder".

Evan
08-18-2008, 09:37 AM
Who needs way covers? These are self polishing. :D

http://vts.bc.ca/pics/farmgrinder.jpg

dp
08-18-2008, 09:44 AM
In regard to the saw in the OP, I'd have at least considered supporting the "out-board" (front) cantilevered end of the main traverse way to convert it to a end-supported beam sufficiently "stiff" so as to form a partial "portal frame" structure. The quality of the "ways" and the stability of the motor and support frame/structure could do with some thought as well.

The size of the grinding wheel will be dictated by the size of the motor stator/housing for optimum use and clearance. I have the same limitation on my T&C grinder when I use it as a surface grinder. I use 7" wheels but the motor housing is 6", so once the wheels are 6" they can only be used for surface grinding where the body of the motor does not have to pass over anything in its path on the grinder table. Other than that, it is fine.

The bottom of the standard motor is flat so as to provide a bit more headroom than if it were round. That diameter issue was a problem even with that type of saw when used to cut wood. Actually, there are a number of well-known problems with radial arm saws that those of us who have used them for a very long time deal with inline and solve almost subliminally. I considered bracing the motor but chose to not add kludge on kludge and ruin the normal operations of the saw. And I wanted to see what it could do, box stock but properly aligned.

The long arm and variable moment, the saw blade offset from the arm's center line, the way the blade orbits the center of the motor for all adjustments, and the climb cut when pulling the cutter through the work are valid concerns.

The consequences affect safety, usability, and precision. Prior understanding affects how it is ultimately used and aids judgment on when it is the appropriate tool. For precision dadoes or rabbeting I use my table saw. For blind slots I use my router table. That is not to say I never use the RAS for these purposes because sometimes it is quite good enough and is often easier than tearing down a setup on a better piece of gear. And I know what to expect, not just a lot of theory and conjecture.



I just hope it can be discussed and developed further for a range of options that might be useful for those that might be considering making, adapting or even buying ("the makings of"??) a cheap "Poor man's Surface grinder".

After having lit off this sh*tstorm and getting nothing but bland theory and no practical hands-on experience I decided to discover for myself what this setup was capable of and what range of work this saw could be used for successfully on metal and I am pleased with what I learned and the successes I had. I was never disappointed with any of the results because I understood ahead of time what to expect.

I'm now better prepared to make informed decisions for when this tool is appropriate and when it is not. Something I did not get from this forum. My greatest regret is that I did not think this would be taken seriously enough to bother with pictures and a write-up, but in fact it is. Just not here.

lazlo
08-18-2008, 10:01 AM
Well said Jerry:


You CAN use a saw as a grinder, if you are not particular about anything but a "ground" finish, and don't need to be able to predictably dust off a tenth or two.

And in any case, the whole reason for the bearing discussion is that the bearings are what makes a lot of the difference between a decent grinder and what you get from using a saw or drill press as an improvised grinder.

oldtiffie
08-18-2008, 10:17 AM
Thanks Dennis.

I had a good "look into" those DeWalt RAS's some time ago as I had my eye on one at an up-coming "Creditors Auction" as I had a lot of use for it. That saw was in "mint" condition and was used by a cabinet-maker etc. It had just about every know "chipper", "Dado", "wobbler" blades and what-ever on a beautiful bench complete with a full dust-extraction system. I was not the only one - the bidding was "red hot" and my limit was well and truly exceeded.

So I licked my wounds and slunk off and bought my "Bosch" 10" mitre saw. As it turned out, the Bosch was a better option for my circumstances and needs.

The Civilian Carpenters shop in the Defence base where I was employed at the time had that very saw same De Walt RAS and I had ample time to discuss its merits and short-comings - and to try it for myself.

I see that you seem to intend to retain the RAS for use as a RAS where-as I had in mind to convert one for use only as a "sort of/possible" surface grinder in a mechanical HSM shop.

It won't surprise you to know that many of the timber yards around here still have DeWalt RAS's on their docking benches - some are over 30 years old and still giving good service.

lazlo
08-18-2008, 10:18 AM
Methinks tiffie, you love to hate this sort of discussion.

Evan, you can think what you damn well like.
You have it 100% wrong.

Evan's right Tiff.

You jump into every one of these threads, posting that the participants should get back on topic, but if you look at the number of posts, your post count is up there with the rest.

Then you usually follow-up with a long-winded post filled with Wikipedia links and scans of that same machinist textbook. :rolleyes:

lazlo
08-18-2008, 10:22 AM
After having lit off this sh*tstorm and getting nothing but bland theory and no practical hands-on experience I decided to discover for myself what this setup was capable of and what range of work this saw could be used for successfully on metal and I am pleased with what I learned and the successes I had. I was never disappointed with any of the results because I understood ahead of time what to expect.

Dennis, did you perhaps re-calibrate your expectations when several responders pointed out that your radial arm saw didn't have precision bearings?

That was the point of this whole thread, IMHO -- that you need good bearings to get a good surface finish and reasonable precision out of a Poor Man's Surface Grinder.

dp
08-18-2008, 10:27 AM
It won't surprise you to know that many of the timber yards around here still have DeWalt RAS's on their docking benches - some are over 30 years old and still giving good service.

I used to work in a shipyard running the electronics shop. This particular shipyard's focus was large old wooden yachts and sailing yachts in particular. I spent every free moment in the carpenter's shop and learned a great deal. The carpenters they had could work miracles in wood from keel repair to building new masts, to spiral staircases.

They had a very large DeWalt RAS there on a 50' bench and many years on it was still there. Next to it was a miter saw. Time and technology moved on but not enough to displace the RAS - only to augment it.

oldtiffie
08-18-2008, 10:36 AM
Methinks tiffie, you love to hate this sort of discussion.

Evan, you can think what you damn well like.
You have it 100% wrong.



Evan's right Tiff.

You jump into every one of these threads, posting that the participants should get back on topic, but if you look at the number of posts, your post count is up there with the rest.

Then you usually follow-up with a long-winded post filled with Wikipedia links and scans of that same machinist textbook. :rolleyes:

Wrong again.

Evan seemed to suppose that he knew what I thought.

I corrected him - just as I am correcting you now.

Yes, I plead guilty to those sins. Whether I am as bad or any worse than for any others is for them to judge for themselves - and to say so - for themselves - if they choose.

I suggest that you stick to just speaking for yourself.

dp
08-18-2008, 10:40 AM
Dennis, did you perhaps re-calibrate your expectations when several responders pointed out that your radial arm saw didn't have precision bearings?

Nope - that was a given. Not only are they not precision, at their age they're often filled with oily sawdust. I didn't start out with unrealistic expectations so much as a desire to discover the operational envelope of the machine in this role. Since I'm so happy with the results I'll continue to explore that envelope. Every machine has one and now I understand a bit more about this one. I also understand that if I buy an identical model it will have different characteristics based on specific wear and mfg tolerances.


That was the point of this whole thread, IMHO -- that you need good bearings to get a good surface finish and reasonable precision out of a Poor Man's Surface Grinder.

Well, that is surely stating the obvious, but I (I started the thread, recall, so I'm well aware of the point :) ) was after more than a nice finish (which finish I got, btw, and I was already happy the with finish I was getting with my shaper). I wanted first and foremost to preserve shop space while expanding and improving my capability. I got that in spades. For fine work or 0.0005" tolerance I'll still send it out but that is not something I normally require.

This solution is light years ahead of the widely used and accepted belt sander and disk sander for similar applications and quite honestly a pleasure to use as is.

lazlo
08-18-2008, 10:42 AM
I suggest that you stick to just speaking for yourself.

I was speaking for myself Tiff.

Evan commented that you appear to enjoy getting tangled in these contentious threads, and I agree with Evan.

That's 100% my opinion :)

lazlo
08-18-2008, 10:45 AM
That was the point of this whole thread, IMHO -- that you need good bearings to get a good surface finish and reasonable precision out of a Poor Man's Surface Grinder.

Well, that is surely stating the obvious

I wasn't obvious to some, who were suggesting that common Chicom bearings out of a drill press would serve...

dp
08-18-2008, 10:50 AM
I was speaking for myself Tiff.

Evan commented that you appear to enjoy getting tangled in these contentious threads, and I agree with Evan.

That's 100% my opinion :)

He's hardly alone in that ailment. It's pandemic. It isn't justifiable to single him out as there is a core group that is the source of the bulk of these contentious threads. Tiffie does spend more time than most at trying to end the contention and/or guide it back on point, and certainly back to the purpose of this BBS. While I don't like so-called net nannies I do agree with Tiffie that we're often abusing the good graces of our hosts.

dp
08-18-2008, 10:53 AM
I wasn't obvious to some, who were suggesting that common Chicom bearings out of a drill press would serve...
Would have been a good thread on it's own rather than a subtext, don'tcha think? There was actually some interesting engineering info that came from it but which ultimately will have little value owing to the slogging through muck factor. Gleaning information should not require hip waders nor be similar in effort to gathering oysters.

lazlo
08-18-2008, 10:54 AM
This week's contentious discussion was whether you can improve the runout of a bearing by compressing it.

Last week's contentious discussion was the price of HSM magazine in Canada, and the definition of "evidence."

The week before was whether solar cells were "Green"

The week before that was Wave Boats.

Hmmm, is there any common theme there? :D

dp
08-18-2008, 10:56 AM
This week's contentious discussion was whether you can improve the runout of a bearing by compressing it.

Last week's contentious discussion was the price of HSM magazine in Canada, and the definition of "evidence."

The week before was Wave Boats.

Hmmm, is there any common theme there? :D

Damn right there is :) A bunch of cranky old men struggling to not be wrong on the internet! :)

Evan
08-18-2008, 11:07 AM
What's a wave boat?


Damn right there is A bunch of cranky old men struggling to not be wrong on the internet!

Almost. What I often see is a few cranky people struggling to prove someone wrong on the internet. Not quite the same.

dp
08-18-2008, 11:11 AM
What's a wave boat?
Recall the boat propelled by wave action thread.



Almost. What I often see is a few cranky people struggling to prove someone wrong on the internet. Not quite the same.

Your honors, I rest my case.

Edit: sorry for the late edit but I hit the wrong button

Evan
08-18-2008, 11:12 AM
Right. That seems years ago.

Evan
08-18-2008, 04:25 PM
Congratulations! You are the unexpected winner of the "FIND A BUG and WIN!!!" serendipity award.

rnum=Math.round(Math.random() * 100000); document.write(''); <a href="http://www.burstnet.com/ads/ad2479a-map.cgi/ns/v=2.0S/sz=300x250A/" target="_blank"> <img src="http://www.burstnet.com/cgi-bin/ads/ad2479a.cgi/ns/v=2.0S/sz=300x250A/" border="0" alt="" /></a

S_J_H
08-18-2008, 05:35 PM
Congratulations! You are the unexpected winner of the "FIND A BUG and WIN!!!" serendipity award.

Yeah I saw it right before I stepped out.
Been that sort of day ...

Steve

J Tiers
08-18-2008, 11:19 PM
BTW.......

Theory? Maybe....

I HAVE a DeWalt RAS..... I have set it up..... I use it. I know entirely too much about it, as I have had the whole thing apart to re-build it

I think it might possibly work as an SG, but the travel on it is rather rough, I doubt if it would do a good job using it on its own carriage bearings......

Now, the person who suggested a separate x-y table I think has a much better idea.... That takes the carriage movement bearings right out of the picture, and leaves a stationary wheelhead. Then the mass of the head will likely make it do OK for shallow cuts. I don't know how you'd set depth of cut, but at least I think it could work.

I admit, I never considered trying it as an SG. I don't think I want to, so I won't have any experience actually doing that.

Ditto with the drill press plan. I know too much about cheap drill presses and have NO desire to try that plan..... I already tried milling that way, and found it was NOT a good plan, for many of the reasons that I believe would also doom the "cheap drill press as surface grinder" plan.

So, I plead guilty. I don't actually have experience of either one as a surface grinder. I have too much respect for the power of the motors to try either plan, although If forced, I'd rather try the saw plan.....

dp
08-18-2008, 11:26 PM
Just an FYI - the grinder wheel was part of the original set of options back in the day. But then just about everything was. Then as now I'm sure it was intended to be used in a limited fashion. I'm far more off-put by the shaper head and dado blades on that dude than I am with the wheel and grinding disks I've tried. Raymond DeWalt had a wicked sense of humor based on some of the products they produced.

The more ya know, the more ya know.

J Tiers
08-18-2008, 11:48 PM
Yeah, I have one of those one-cutter molding blades with mine, and I am too chicken to use it..... That thing just scares me, looks too ready to launch a piece of wood.

Also has a 3 cutter version, but not very many different cutters..... the one-blade unit has a ton of 'em. haven't used either, actually, but the 3 cutter looks a bit safer, if the term can even be used with reference to it!

oldtiffie
08-19-2008, 12:27 AM
Yup.

The "wobbler" wheel/blade set between two tapered disks (similar to those tapered washers used for taper-flanged (hot) rolled beams) where it wobbled from side to side for trenching was an eye-opener. So were the dado multi staggered 2-toothed dado/chipper cutters between twin saw blades - in action for trenching were a real concern. It was classic "gang-milling" like you'd never see on a milling machine!! Just "hang on, brace yourself on the "de-Walt" RAS, don't hesitate - and into it!!!

The one machine I did stay well away from was an "Industrial" big high-speed vertical spindle moulding machine. There were too many carpenters and cabinet-makers who were missing parts of fingers on that machine for my liking!!! "Breaking down" saws - for big timber flitches and baulks etc. - were not far behind.

I have just about every "Triton" (Australian-made) tool as well - I will post pics later as they could be the basis of a "poor man's surface grinder" as well.

That "swing grinder"
http://vts.bc.ca/pics5/swing1.jpg
that Evan posted at
http://bbs.homeshopmachinist.net/showpost.php?p=374628&postcount=80
had me re-thinking it. It does look very substantial and would cover quite a sizeable area. I had a good down-feed as well. It seemed similar to the mill on my 3-in-1 which can both "swing" or be locked and use my lathe slides and feeds. That head has a very accurate fine feed on it as well. It has 4 belt-driven speeds. A "T-slotted" table can be bolted to the cross-slide in lieu of the compound slide.

http://i200.photobucket.com/albums/aa294/oldtiffie/AirSmith11.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/AirSmith10.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/AirSmith09.jpg

This one of Evan's has real promise:
http://vts.bc.ca/pics5/swing3.jpg

This one of his addressed the basics of a possible linear guide/slide pretty well too.
http://vts.bc.ca/pics/farmgrinder.jpg

More later.

bruto
08-19-2008, 09:59 AM
Yeah, I have one of those one-cutter molding blades with mine, and I am too chicken to use it..... That thing just scares me, looks too ready to launch a piece of wood.

Also has a 3 cutter version, but not very many different cutters..... the one-blade unit has a ton of 'em. haven't used either, actually, but the 3 cutter looks a bit safer, if the term can even be used with reference to it!There was a special guard made for the molding cutters which helped a little to make them less scary. I don't have it, but wish I did. Three bladed ones are actually pretty comfortable if the machine is set up well, but I've never dared use the original type that were made with a single twisted piece of steel.

If you're seriously contemplating using a molding cutter, new inserts are still being made for some brands. I've lost the link now, but there's a place in New Hampshire, I think, that makes both these and high speed steel shaper cutters for pretty reasonable prices.

I don't like the "wobble" dado blades for a radial arm, because it's almost impossible to visually line up the blade with a line. The tooth profile isn't very safe anyway. Stacked dadoes work much better.

J Tiers
08-19-2008, 08:36 PM
I'd probably MAKE special cutters....... why else would I have a shop?

Besides, I'd only do it to reproduce old moldings.... my house (you in the UK keep quiet) is pushing 80, and *styles have changed*, to say the least............