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gundog
07-20-2006, 12:41 AM
Here are some tips for indicating in a part on a three jaw chuck. I keep reading about guys saying their three jaw chuck is not concentric and has too much runout. A friend of mine an old machinist showed me this I am a home shop self taught guy so I thought it was cool, so I am going to share it with you. If you are an experienced machinist this probably is a waste of your time or maybe you can add something for the rest of us.

The first picture is a piece of seamless pipe I picked up for another project and it is pretty round or concentric so I decided to use it for this demo.

http://img.photobucket.com/albums/v292/millnut/DSC03340.jpg

The second photo shows me setting up the indicator on the end of the pipe. Snug up the chuck but don’t cinch it down yet. Rolling the chuck by hand to find the low point and setting zero there.

http://img.photobucket.com/albums/v292/millnut/DSC03341.jpg

The next photo shows the high point about .012” out some would say bad chuck or the pipe is not round.

http://img.photobucket.com/albums/v292/millnut/DSC03342.jpg

The third photo is me tapping the high side with a small soft hammer. Then roll the chuck and keep tapping the high side until it is concentric. Then snug up the chuck and roll it again might need a love tap or two just don’t beat it with a BFH or you might damage your chuck. If the part is not round it will never indicate in but it will be closer than just chucking it and going from there.

http://img.photobucket.com/albums/v292/millnut/DSC03343.jpg

I was able to get this part from .012” out to .001”. If you need better than that better dig out the 4 jaw.
If this was any help great it has helped me.
GD

kap pullen
07-20-2006, 08:28 AM
Gun Dog,

That's really neat.
How does your friend make it run true at the jaws?

The usual procedure I learned is true it at the jaws, then tap the end true.

It can be trued at the jaws by putting shims at the high point of the runout.
This is a less than ideal solution being somewhat trial and error.

I made the chuck/backplate locator rabbit .010" loose so I can true things up by tapping the chuck body to true the part at the jaws, and tightening up the chuck retainer bolts, then tap the end true like you said.

That works like a poor mans adjust true chuck.

Kap

smagovic
07-20-2006, 08:36 AM
So what do you suggest, that everytime we mount a piece of metal we do the tap dance? It seems that this is the only way to get it right though. I think it also depends on the quality of the chuck, do you agree? Thanks. Vic

gundog
07-20-2006, 11:31 AM
Kap this works for me right at the jaws also. Before I learned this I thought my chuck was bad and was considering replacing it. I am not trying to say this is a fix all just passing some of my very limited knowledge to some guys who may not know this.
GD

A.K. Boomer
07-20-2006, 11:34 AM
Or you could re-bore your chuck jaws, theres a multitude of different ways of going about this, some better than others, try to mimick same as work conditions...

nheng
07-20-2006, 11:54 AM
One kinda related 3 jaw tidbit is that many quality 3 jaw chucks will have one of the key holes marked or only have a single key hole to begin with. This is the hole to use when tightening as it "loads up" the force on the scroll as it was when the jaws were ground at the factory. It can/will make a multi thousandths difference. Den

Evan
07-20-2006, 12:12 PM
Boring the jaws on a 3 jaw scroll chuck isn't a fix for centering. The usual source of inaccuracy is the scroll itself. You will usually find that the chuck centers better at some diameters than others. This is because of variation in the scroll.

There is no fix for this as it is dependent on the scroll. Having to tap the work as shown to center it usually means the jaws are bellmouthed and aren't holding the work securely. In that case boring (grinding) the jaws may help but it won't improve the accuracy of the scroll.

The 3 jaw isn't meant for accurate centering of work. It is used to hold work where the concentricity, if required, is produced by the sequence of operations.

Forrest Addy
07-20-2006, 12:28 PM
So-- why are't we using a 4 jaw and doing the same thing getting better concentricity and grip?

Yeah, I know, this thread wasn't started for the curmudgeon could get in a growl but there's some points.

Most 3 Jaw chucks after a few mild wrecks have bell mouthed jaws. I'm not at all surprised that one could knock 0.012" of TIR out of that hunk of tubing 3" out from where it's gripped.

A three jaw chuck is not a universal solution to lathe work holding.

Here's the rule for three jaw chucks: they are used for work where reliability of grip and second operation concentricity is not a paramount concern and where lobed diameters can be tolerated. In all other cases use soft jaws bored to suit the work, a collet, a face plate, or a four jaw chuck.

Adjustable three jaw and six jaw chucks like the Grip-Tru can offer first rate concentricity so long as they are undamaged. It's not wise to even part off work in them for fear of a wreck. For all its mass and apparent strength a three jaw chuck is truely delicate.

BadDog
07-20-2006, 01:22 PM
My newbie ignorance surfaces again. Learning something new every day is good, but since I started my descent into darkness (aka machinist hobby) I still find something new in most every post. :D

I knew about tapping the work piece to help align/true, I knew about the 3 jaw limitations, different TIR at differing diameters due to scroll, and boring soft jaws for specific diameters (BTW, to true up hard jaws, bell mouth or staggered, would require a tool post grinder or similar), but I stumbled on the last part in Forrest's post.

It's not wise to even part off work in them for fear of a wreck. For all its mass and apparent strength a three jaw chuck is truely delicate.
I was under the impression that "wreck" or "crash" indicated chuck or work piece (spinning stuff) impact into tool, tool holder, cross/top, or carriage (non-spinning stuff). How does this intersect with "not wise to part off for fear of a wreck"? I understand you can stall or get insane chatter, or even break a tool parting, but how would that hurt the chuck? Or is it the potential for a Bouncing Betty getting into the chuck?

Evan
07-20-2006, 01:39 PM
If parting something sturdy like a 2" dia steel bar and the tool digs in something is going to give. First the tool most likely but the forces on the chuck jaws are high and not balanced. Imagine putting a foot long bar in the chuck and giving it a good whack on the far end with a hammer. Not good for the jaws.

J Tiers
07-20-2006, 01:40 PM
4-Jaw.....

THE chuck to use most of the time, unless some reason not to. Totally agree with Forrest.

Easy enough to set up, even by eye, that there is NO reason not to. If you find it hard, force yourself to use the chuck for a week. After that you will hardle notice it.

By the time you mince around shimming or tapping your part in a 3 jaw until the part is in straight, you could have set up the 4 jaw and be done with the job.

Then also, CONTRARY TO EVAN's STATEMENT.... MOST 3 jaw problems I have seen that were significant in terms of concentricity, were due to bell-mouthing, or worn slots, etc, not the scroll. And, I have used quite a number of 3 jaw chucks of various vintages (no new ones though!).

I think the scroll, although admittedly a weak point, is unfairly blamed for problems that may be elsewhere. If the scroll causes 0.012 out-of-position, you could see the scroll problem by eye, a bend, gouge, etc.

That being the case, tapping a part into alinement can be flat silly..... because......... what if you DO get it straight? It still may not be held by a solid jaw.... might just be "nipped" at one spot near jaw base if the jaw is belled or cocked.

Anything but the lightest cut risks pushing the part off-concentricity, causing a "dig-in" (the "wreck" Forrest referred to) as the part moves in the chuck.

Who wants to suddenly be taking a cut 0.025 (or more) deeper than you expected when the part isn't securely held?

With most "hobby" machines, that will jam the drive, maybe bending things. It sure may chop off the cutter short if it is a threading tool, etc, etc. If the compound is stuck out too far, it may get broken off short (Atlas, mostly)

Evan
07-20-2006, 01:49 PM
CONTRARY TO EVAN's STATEMENT.... MOST 3 jaw problems I have seen that were significant in terms of concentricity, were due to bell-mouthing, or worn slots, etc, not the scroll.

I said it was due to bellmouth, not the scroll. What I also said is that centering inaccuracy is due to the scroll. If the chuck is in good shape, mounted properly and the jaws are not bellmouthed then the scroll is the only remaining source of centering inaccuracy. Scroll inaccuracy is shown by variation in centering accuracy at different diameters. That is easy to test. Grinding the jaws won't fix this except at the specific diameter they were ground at.

BadDog
07-20-2006, 02:49 PM
If parting something sturdy like a 2" dia steel bar and the tool digs in something is going to give. First the tool most likely but the forces on the chuck jaws are high and not balanced. Imagine putting a foot long bar in the chuck and giving it a good whack on the far end with a hammer. Not good for the jaws.
That I can see, but I've always parted off next to the jaws, so it's generally just a stall or broken parting tool. I guess it's mainly the term "wreck" in a context that does not mesh with my intuitive understanding/definition.

Evan
07-20-2006, 02:55 PM
Unless I have no other option I part off with the bandsaw.

BadDog
07-20-2006, 03:20 PM
As do I. Well, maybe I wouldn't go quite so far as to say "no other option", as I sometimes part off to reduce scrap, but in general I agree. However, I'm hoping the new lathe (with much greater rigidity and it's option to part in reverse due to L00) will make parting off less of an "experience". ;)

Sorry for the short side trip. Now back to our regularly scheduled topic... :D

BobWarfield
07-20-2006, 03:43 PM
Clearly need to add another entry in the long list of "religious topics."

So, 3 jaws are bad, 4 jaws are just as easy if you use them for a week, but we still have tons of experience with those lousy 3 jaws, and we don't like parting off at all.

I always enjoy these little scuffles, at least once I learned not to get too seriously wrapped up in them and to view them as entertainment. Sorry, don't take offense guys!

I think the tip is a good one. I have no fear of my 4-jaw and use it often, but my 3 and 6 jaws are just more convenient if I don't need the 4-jaw (for the reasons Forest laid out). I tend to prefer the 6-jaw for reliability of grip (that was a tip from Machine Shop Trade Secrets), but won't risk it if the work seems likely to be dicey for some reason. Using this tip, I can envision a fast couple of light taps making a big difference and saving me a little bit of time versus swapping chucks for the 4-jaw. With that said, I don't think I'd try it on my 6-jaw, which I tend to baby, and wouldn't want to tweak the jaws or scroll on. It's a Set-tru type anyway.

I would also say that I really like turning between centers, which I assume is covered under Forest's "faceplate" category, though I use a face turning rig to do so.

I envision this tip being handy if I am not particular about concentricity, but just want to remove the minimum of stock, perhaps just for finish reasons (hit exactly this situation recently making my vise stop).

I find "tapping in" to be an essential skill around the shop, and have an assortment of small to BIG mallets to assist in the chore. It seems to me that one can develop a feel in terms of whether the tapping is performing a slight adjustment, moving a part to a potentially disasterous partial grip, or starting to tweak your tooling in a damaging way. I find the smaller hammers, lighter taps, and patience helpful in assuring one doesn't cross the line there.

As for parting off, my troubles went away when I started using an Aloris insert tool to do it. The process is always extremely smooth with little drama at all. I would not consider a bandsaw for the task. If nothing else, the surface finish from the Aloris is so nice I have to do little except get rid of the little bit of nib with a little hand stoning.

Everyone hating parting should therefore spend a week parting with their 3-jaw chucks. The floggings will continue until morale improves!

Cheers!

BW

Millman
07-20-2006, 03:53 PM
[[Everyone hating parting should therefore spend a week parting with their 3-jaw chucks]] Yes Bob, that should be mandatory punishment.

CCWKen
07-20-2006, 04:05 PM
Good post Gundog and nice descriptive pictures of the process. I agree with the others that the procedure can just as well be spent truing the part in a 4-jaw though. One more thing--Lift your indicator plunger before tapping the part. The jarring is hard on the tool. ;)

I'll add my argument here. I see more wear on the scroll bearing not the scroll or jaws. These are normally hardened and wear against the cast iron (or semi-steel) bearing face. The wear on the scroll bearing allows the scroll to move sideways and bind or misaligned the jaws.

The jaw track is the next area to check for wear. It's rare to have bell-mouth jaws unless the user is a gorilla or the chuck has had a hard crash. I've got a TOS chuck that has replaceable jaw tracks. The same "rebuild" could be done to most any chuck. Before I would grind jaws, I would check these areas of a chuck. Grinding jaws should be the LAST attempt at truing up a chuck.

thistle
07-20-2006, 04:43 PM
My 15x50 lathe came with a 3 jaw that had been tapped.

some one must have tried to adjust the run out by slacking the bolts at the back of the chuck, tap tap tap,nothing moved. wallop wallop wallop.still no move.
and so on through to clang smash kabang ect.

wouldnt adjust because the chuck is a direct mount , no back plate moron .....
result trashed chuck.I need a 10 inch D1-6 3 jaw chuck.

I never use it ,always the 4 jaw , slow yes but maybe im learning something.

pcarpenter
07-20-2006, 05:45 PM
I have read threads about how awful three jaw chucks, especially cheap ones, were and concluded that I had better start learning to use a 4 jaw. On the other hand, I find I use my lathe a lot for chucking something up to clean it up quickly and thought about how annoying it will be to make that chuck swap all the time. Truing something in a 4 jaw so I can hit it with a file for 10 seconds doesn't make sense, and swapping chucks back and forth for a ten second job is a pain.

So....I started checking the conventional wisdom and found that I had .00025 runout on a ground dowel pin chucked in my three jaw?? I rotated the pin to see if I was seeing cancellation or something....no dice. Is this because I have a relatively new chuck? Maybe. It is a Chinese lathe mind you. On the other hand, I ran another quick experiment and just tightened the chuck from one screw, relying heavily on the scroll and suddenly I had over .003 runout. I went back to working all three screws sort of carefully and back to .00025 or so. It adds maybe 20 seconds to work around the three screws that drive the scroll and this seems very worthwhile....certainly quicker than centering an item in a 4-jaw independent chuck even if I was good at it (which I am not). Is this unique, or is it likely that part of the general assumption about a three-jaw chuck is really that it is a *scroll chuck* and that we tend to do all of our tightening from one screw? If a little care is a solution to part of the problem, it could sure beat the inconvenience of the 4 jaw for everything but the very most critical, or irregular shaped, work.

Paul

nheng
07-20-2006, 06:23 PM
Paul, I believe that a single keyhole is specified as THE one to use on 3 jaw chucks because from whichever hole you use last, the pinion places tangential and radial forces on the scroll, the latter pushing it away from that hole. If the jaws are then ground in place at the factory, then the best repeatablity will come from using that single keyhole. I've seen this on Rohm, Bison and Emco chucks as they are all marked this way.

I may have stones cast upon me as a sinner but for any round work, I find the 4 jaw a PITA. Maybe I just need a smaller 4 jaw but they seem to have aggressive jaw patterns, requiring additional shims to protect the work from them. They also seem to be built a little looser and this can require additional shimming to get a part on axis over its length.

Please be gentle as I just got out of the hospital ;)

S_J_H
07-20-2006, 06:34 PM
Everyone hating parting should therefore spend a week parting with their 3-jaw chucks. The floggings will continue until morale improves!

I have never quite understood the difficulty about parting I keep reading about? Guys must be trying to part 5" stainless or something on a import 9x to have all these woes.

I avoided the 4 jaw when I first started to use a lathe. It just seemed like a lot of work and I always went for the 3 jaw. Most people go for the easiest method of anything and I am no different. But I quickly learned the importance of proper setup and the few extra minutes of indicating the 4 jaw was well worth my time.
After a little time spent with the 4 jaw it is fast and easy to adjust to less than .001".
But as stated many times you just want a quick fast chuck to use for something simple and then the 4 jaw is a PITA.

How about those 4 jaw combo chucks like this? http://www.brassandtool.com/Chucks-Lathe.html ( about 2/3 down the page)

I could see one of those coming in handy now and then but I have heard little discussion about them.

Steve

Evan
07-20-2006, 06:43 PM
I have no problem with parting but since I will have to true up the parted face in a second setup anyway it is much easier and safer to use a saw.

BadDog
07-20-2006, 07:03 PM
Your right, I've been parting on my 9x20 which lacks the rigidity or power to effectively part off without jumping through hoops. I've done 1" and such with no problems, but anything of consequences chatters like it's coming apart. It's just easier to "part off" with the saw within 20 thou or so, then face it off. Or it won't fit through the head stock so I have no choice. I'm hoping with the large spindle hole and much greater rigidity of the Rockwell will make that a non issue in the future.

As for the "single keyhole", I haven't heard that. In fact, I generally snug it up on one, use DTI and bump if it's important, then finish up with the other two, and check again depending on requirements.

And on 4 jaws, I also generally don't use them on round stuff because I usually don't care that much. Right now, set up on my 9x20 but not run is the intermediate shaft that got damage by washed out bushings on my 11x37. I’ve chucked the end that is pinned in the cast bracket in my 3 jaw, and the other end is mounted in a live center using the original center drill. All I need to do is get the scoring cleaned up and if it’s a few thou off concentric with the pinned end, who cares? All I need is a specific size and very smooth finish, so why go to the trouble? And the vast majority of my stuff is like that, where all the “must be concentric” stuff is turned at once without a rechuck, or it just needs to be round, or faced, or whatever. So my 4 jaw rarely gets used at all other than not round stuff or the very rare occasion where I do care about concentricity with existing features...

smagovic
07-20-2006, 07:17 PM
Gundog, thank you and all of the people whom contributed to this thread. It was very educational. I had a problem a week ago, and I wish you guys 'did not wait' with this analyzes until now. This is one of the classics.

There is however one serious problem with all of this. About 3 or 4 days later this thread will be so far down off the screen that it will be lost for ever. There are perhaps other classics down off the screen and when a new person comes they never make it that far down to read it. I was wondering if there is a way, as part of the BBS, to establish some kind of a depository where these classics could be separately stored, and newbies then could go there and rumage only through a small single subject, valuable- educational threads. Many thanks. Vic

P.S. By the way would it help if the chunk of metal in question, would be supported by the tail when being installed? That should help to install it in a more centered way. never mind, just trying to find a short cut/compromise. VS

S_J_H
07-20-2006, 08:41 PM
Your right, I've been parting on my 9x20 which lacks the rigidity or power to effectively part off without jumping through hoops. I've done 1" and such with no problems, but anything of consequences chatters like it's coming apart. It's just easier to "part off" with the saw within 20 thou or so, then face it off.

I have a 9x20 also and it can do the job with a little modifying. The first thing I did when I got it was to remove the compound and mill a 4"x4" x 1" hunk of cast iron and add a 100 series tool post to replace the compound slide.I have never even tried turning with the compound slide on. I took one look at it and said you must be kidding.I'll put it back on only when needed.
Parting, grooving and cuts .125" deep are no problem now. I was boring using hand feed taking a .200" DOC in 6061 yesterday without any chatter to quickly rough out a 2" hole.Pretty impressive for this lathe IMO. Put a corner rounding router bit used for wood in the tool post to form cut some rounded corners in the 6061. Again not an issue and this was a 1/4" radius bit.It's all about rigidity. Gotta make that little 250lb buggar rigid!
I realize there should be no need to remove the compound on a good lathe to be able to have good performance. But this is a 9x and that's what it takes sometimes.
A little imagination and the 9x is a capable hobby "lathe like" machine.:D

So anybody use one of the combo chucks that can scroll and also be adjusted independently?

Steve

Wareagle
07-20-2006, 11:32 PM
Reading all of this about the three and four jaw chucks reminded me of something that a machinist friend had told me a while back, and that was to avoid parting off with diameters over 1 inch to avoid all of the stress on the chuck (three or four jaw) and bearings.

So this brings up a newbie question: In my mind, the farther away from the chuck (3 or 4 jaw) you are with the parting tool, the more stress the jaws take, regardless of diameter; would it be safe to part off 'small' stuff close to the chuck, or is it a better practice just to use other methods, meaning a saw?

gundog
07-20-2006, 11:38 PM
I have parted off with my SB 10K many times either close to the chuck or with a steady.
GD

J Tiers
07-21-2006, 12:03 AM
IMO / IME, the most troubles concerning parting are from a small number of causes.....

A machine problem.... in my case an old Logan 10" with non-preloaded bearings.... after adding preloading, I PREFER to part off rather than saw, not to mention that sometimes you HAVE to.

Not getting the parting tool dead straight at 90 deg (250mC) angle.

Parting too far from the support.

Having "hook" or other non-flat cutter top that exerts a pull on the part as it cuts.

Fix those things, and life is far better.

There IS stuff too big to part, for which you want a bigger, more heavy and rigid machine.

It is well to remember when you have a 300 lb 10" machine, that serious 10" machines can weigh well over a ton.... and there are bigger machines for which a 7" round is like 0.750" in yours.

S_J_H
07-21-2006, 01:12 AM
Having "hook" or other non-flat cutter top that exerts a pull on the part as it cuts

well you sure are right about that! I just spent an hour or so grinding a really nice grooving tool to cut some fins on that Stirling engine I am making.
I have made many grooving tools and never had a problem until tonight.
I had never tried this before but thought a little positive top rake might make it easier to cut aluminum.
Only gave it 5 degrees but for a total of .75" long so it got pretty narrow at the end.
Tried it out on a 1.5" round and I knew right away I made a big mistake. It was making chips chip breaker style and wanted to chatter real bad unless I really fed it in fast and took a deep cut. Then it worked and cut very quickly. But it was not long before I heard "tink" and it snapped off.
Oh well lesson learned.
Arghh.. I may just cut those fins with a rotary table and slotting saw now.

Steve

Evan
07-21-2006, 03:38 AM
I don't quite follow your description of the tool you made. A normal cutoff tool is hollow ground so it is thicker at the top than at the bottom so it has clearance on both sides. For aluminum you need positive rake, about 10 to 15 degrees or the tool will grab or not cut well.

These fins were cut with a small cutoff tool on my SB9 with the tool held in a quick change holder on the compound. The cutoff tool has about 15 degrees positive top rake ground in. You need some positive rake so that the widest part of the tool is the cutting edge.

http://vts.bc.ca/pics/fins1.jpg

J Tiers
07-21-2006, 08:35 AM
"Hook" would be grinding so that there is back rake.... the tool is relieved on a down slope from the cutting edge back into the body of the tool.

I have several cutoff tools from boxes of "misc" that some moron ground like that.... I would have to take off about 1/4" to get past it. I have never used them, too much hassle to grind back or break off.


BTW, I have ground the jaws on three 3jaw chucks... Far from the horrific poor results the doomsayers predict, I have found that they repeat as well as any 3 jaw chuck at any diameter I happen to use them at.

Not surprisingly, they are naturally the best at the diameter they were ground at... but they don't magically go 50 thou off at all other points... They are probably within 3 thou or so everywhere... certainly acceptable for what they are...

S_J_H
07-21-2006, 09:51 AM
A normal cutoff tool is hollow ground so it is thicker at the top than at the bottom so it has clearance on both sides.

My description was poor.I had the right side and top clearances but I think the main issue was the back rake that extended for 3/4" which really weakened the tool bit and caused it to be unstable.
Looked like this pic but extend the rake further into the tool and you can see how weak it was.
http://mmu.ic.polyu.edu.hk/handout/0102/02_f7.jpg

I have cut plenty of fins so know the procedure pretty well. Somehow I made a lousy tool last night and I think it had to do with the back rake for such a long distance.
I should have used a holder with built in angle instead.
At least I think that was the major fault. I'm no expert on grinding grooving tools.

I ground my jaws in my 3 jaw in an attempt to true it up a bit. It did not seem to help much, but my 3 jaw is junk though.
Steve

Evan
07-21-2006, 10:11 AM
Positive rake is needed for aluminum, not recommended for steel or brass. Aluminum doesn't cut well at all with zero or negative rake as it will load the cutting edge.

A.K. Boomer
07-21-2006, 10:50 AM
"


BTW, I have ground the jaws on three 3jaw chucks... Far from the horrific poor results the doomsayers predict, I have found that they repeat as well as any 3 jaw chuck at any diameter I happen to use them at.

Not surprisingly, they are naturally the best at the diameter they were ground at... but they don't magically go 50 thou off at all other points... They are probably within 3 thou or so everywhere... certainly acceptable for what they are...


I think this is a correct analogy,,, My suggestion was of coarse if the chuck was experiancing the same deviation in all modes, in this case it would mean that one of the jaws was off, Nothing against evans statement because it can be true --- but hopefully its obvious to everyone that if a chuck does not behave the same in other positions the problem lies elsewhere (other than the jaws) I really dont know of any machinist that doesnt know thier chuck this way, and if you get a brand new one and its off then check it in a variety of positions before making a correction....
You will also find this --- Jaws change more over the years, thier surface area is small as compaired to the worm, if both are ground correctly but after many years their is deviation then its most likely due to one or more of the jaws either wearing funny in its slot or wearing at thier teeth, they are both hardened (the jaws and the worm) but one see's the same "geared" surface every time its tightened (jaws) while the other changes its position with different size stock......

A.K. Boomer
07-21-2006, 11:13 AM
curious how many of you fella's have tried mixing your three jaw teeth up and then turning some scrap stock and recording the results, you can get a variety of different eccentric offsets and once recorded might come in handy for something down the line? as long as you respect the maximum distance you hang the furthest jaw out and dont go to wild with the RPM's i dont see anything wrong with this,,,,,, I bet you Millman has done this before, there are book fella's and then there are field fella's,,, Millman is a field fella,,, if he hasnt tried it he's probably gonna:p

smagovic
07-21-2006, 02:02 PM
On my chuck you cannot do that. Each jaw has an assigned position. If you mix them they never close. Some chucks, I gather the better ones, have the jaws numbered. On my chuck I have to line up my jaws next to each other and see which one go in first and so on. Take care. Vic

Evan
07-21-2006, 02:13 PM
They may not close but that isn't his point. They could still grip something with a predictable eccentricity. I have not considered this before and it might be useful, or not. I will have to try it. It could be very handy for making a cam.

smagovic
07-21-2006, 02:13 PM
I have a question which perhaps Evan can answer for me. I have difficulties to figure out what is the difference between the rake angle and inclination. I have a booklet here, that mentiones that to see the rake angle one has to look at the cutting tool from the side, and that I understand. I have not heard before about the inclination in connection with a cutting tool. They say that to see the inclination, one has to look at the cutting tool from the front. That is where I get lost. If I look at the grooving tool, for instance, from the front, I see a horizontal line, no angle. If I look from the side I may see a line going down toward the body of the tool. That would be the rake angle measured against a horizontal line. Is there a better explanation as to what inclination is, and how I can see it? Both angles mentioned have higher values for aluminum as Evan mentioned. Thanks Vic

Evan
07-21-2006, 02:17 PM
Looking from the front if the cutting edge is not inclined it has no inclination. If it is inclined so that one side is higher than the other then it has inclination. This is the same as rake but this rake is measured from one side of the tool to the other instead of from front to back.

smagovic
07-21-2006, 02:20 PM
Evan, I thought that is what we have 4 jaw chucks for that we can make cams. If you mixh the 3 jaw chuck jaws, you have only very few combinations, and positionvise, those combinations will not change. You would be able to make only, say, 3 different cams of not your choice. The choice would be given by the gap the jaws end up appart when mixed. But, again it is my view of it and I can be wrong. I think it happened before. Vic

smagovic
07-21-2006, 02:26 PM
Thanks Evan, obviously I picked a wrong tool bit - the grooving bit- to look for inclination, there is not one. If I have picked some other bit there could be one. I see. Thanks.

BadDog
07-21-2006, 02:42 PM
Can't delete on this board?

Evan
07-21-2006, 02:57 PM
Vic,

Suppose you don't have a 4 jaw chuck? I do but not everyone does. Yes, you can use shims but still it might be a useful trick even if you only ever use it once.

smagovic
07-21-2006, 03:32 PM
Evan, you have a good point. I did not think that far. I tell you for a guy who goes to supermarket and claims he does not remember what to buy until he is there (I understand I operate the same way), you answer all those questions faster than I can write them. Have a nice weekend. Vic

Evan
07-21-2006, 03:42 PM
Have a nice weekend.
Thank you, I intend to, you as well. It's getting hot here, supposed to hit the mid 90s this weekend here and as high as 110 some places in BC. That means I get to work in my shop in the basement where it is nice and cool. :D

I do plan on working up a sweat though. I plan on melting up 75 pounds of lead this weekend.

BillH
07-21-2006, 03:53 PM
I listened to Forrest Addy and use my 4 jaw when ever It needs to be real close.
ALSO, I learned somethign by reading this thread, on my bison chuck, THERE IS A MARK! I'll be damned! Im only goingto use that key hole.

smagovic
07-21-2006, 03:54 PM
Evan, we had two nice days, today was supposed to be another one, but it is humid and raining on and off. What are you making? Bullets? I have a neighbour, he is a gun fanatic, and he makes his own amunition all the time. Well do not burn yourself, I have done it as a kit and had a little hole in my leg, it took a while to heal it. I tell you that 3 jaw chuck, was a best thread in a month. Very educational. Now, I am going in the basement too.Vic

Evan
07-21-2006, 04:07 PM
No bullets. I'm casting a counterweight for my mill. While I am at it I will cast up some small ingots to use in the shop. I also have about 25 lbs of bullet lead which I will cast up into a better shape ingot to use some for making a lead hammer.

S_J_H
07-21-2006, 05:30 PM
As I was driving to work this morning it hit me. Why in the world did I grind a 3/4" length of back rake?
Just wasn't thinking clearly last night.
I have made 8 rib automotive supercharger pulleys using a ground down screw driver bit. You would think I would know how to grind a simple grooving tool by now. I guess not. I'll go grind another one my normal way, cut some fins, marvel at how shiny and nice they look and then it's Tequila time.

Steve

smagovic
07-21-2006, 08:15 PM
Evan, as soon as I hit the submit key I immediatelly realized that you are going to cast that dumbell for the milling machine. Good luck with it. I hope it works (there is no reason not to). Vic

smagovic
07-21-2006, 08:22 PM
SJH, you just proved to yourself that you are a human. We all do silly things from time to time. Some of us do it more frequently than others. What is important is that we remain capable of recognizing when we screwed up. You will remember this one perhaps for the rest... Have a great tequila time! I am having a couple of glasses of vine myself right now. For medicinal purposes only, of course. You see I did not do anything today, so I did not screw anything up. That is one way (sometime the only way) to avoid it, but then you do not have any fun. Vic

A.K. Boomer
07-21-2006, 08:41 PM
Evan, I thought that is what we have 4 jaw chucks for that we can make cams. If you mixh the 3 jaw chuck jaws, you have only very few combinations, and positionvise, those combinations will not change. You would be able to make only, say, 3 different cams of not your choice. The choice would be given by the gap the jaws end up appart when mixed. But, again it is my view of it and I can be wrong. I think it happened before. Vic


its very limited and i also think its nowhere near as sound due to the jaw grips being on there edge, it could definitly throw a chunk of steel at your forehead if your not careful and if you get way out with one jaw things could really get scary, i might try it on delrin sometime or something like that, I was just thinking outloud, I know somewhere out there one of you guys have tried this,,, if your still alive post back and tell us how it went!

lane
07-21-2006, 10:58 PM
It took 9 post but it was all well said. Three jaw chucks are like dail calipers JUST FOR CLOSE thats it . You wont it right wse a 4 jaw or collett.

S_J_H
07-21-2006, 11:05 PM
smagovic,
Thanks for the encouraging thought. I actually do not mind making mistakes. I always make it a learning experience. But hopefully not to very often!

Well I ground a new grooving bit. The problem is these grooves are .125" wide and that is quite a large tip to plunge with this import 9x lathe on 3" diameter stock. So I had to get fancy with the tool and make an anti chatter tip.
I have made these before and they work great. Just a little extra work to make.
The bit was ground with a 2' included angle on the top of the bit and 6' included side wedge angle and 1' back rake for good measure. Then a .020" wide slot by ~.020" deep centered at the cutting tip.
For the guys who have not used this type of cutter before they work very good.
When starting the cut it makes 2 narrow chips and that pretty much keeps chatter away and lets you easily and smoothly begin the groove, form cut or parting operation..
Once the tool has cut into the work a bit, you can really lay into it and it will produce a single chip with a deformed center. The tip slot provides sort of a key way for the tool bit which keeps it stable and locked to the part which drastically reduces chatter.
I cut these grooves at 300rpm and not a trace of chatter. Also if made right it will not buildup. This is 6061 which we all know is the stringy aluminum. The tip was clean as a whistle after making these grooves.
Before grooving this part I tested it and parted 1" stock like butter.
Try this type of tool bit if you are having difficulty parting. Obviously it is limited to wider tip sizes though.
Here's some pics because I don't explain things to well sometimes.
So now it is really Tequila time and I'll finish this part up tomorrow.:D
Steve
http://i109.photobucket.com/albums/n48/S_J_H/Stevie187.jpg
http://i109.photobucket.com/albums/n48/S_J_H/Stevie186.jpg
http://i109.photobucket.com/albums/n48/S_J_H/Stevie190.jpg

Millman
07-22-2006, 03:13 AM
SJH, now that is an old trick, that I'm sure most guys will try to emulate. Saves a lot of headaches for deep grooving and parting. Great pics. That design eliminates a LOT of chatter and tool breakage.

smagovic
07-22-2006, 07:58 AM
SJH, I am glad that you had a will to hold off on that tequila. I am also glad that you are not one of those guys who has everything copyrighted (ha,ha). I never had any need for making a lot of grooves, but I hope this will change soon. I printed your implement so I do not forget. Very nice. Thank you for sharing. Vic