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donf
04-14-2012, 10:43 AM
http://i228.photobucket.com/albums/ee288/earlysb1/for%20sale/077369b9.jpg
This popped up used - its supposed to be an old 18x18 calibrated surface plate with legs, but look at the big dings! They are asking $75, but after I saw the dings in the picture I am thinking a 12x12 granite one from shars for about the same price shipped is looking pretty good! I have very little machine tool knowledge so I just figured I would get a second opinion in case I was over looking something.

tdmidget
04-14-2012, 10:58 AM
Forget it. IF it ever was a surface plate, it ain't now. That hanger thing looks very out of place. To be a surface plate, it would have to be scraped and then to maintain it's flatness, scraped or lapped on a regular basis.
Granite is cheaper, more durable and easier to maintain.

MotorradMike
04-14-2012, 11:05 AM
Are they claiming it's calibrated now?

donf
04-14-2012, 11:09 AM
No not now - this is the ad. http://portland.craigslist.org/clk/tls/2949531194.html
Thank you for the feedback!

vpt
04-14-2012, 11:15 AM
Honestly I wouldn't mind having something like that for bolting down parts for welding.

donf
04-14-2012, 11:25 AM
Honestly I wouldn't mind having something like that for bolting down parts for welding.
This was an old welding project with surplus 80/20 t-slot purchased off ebay when aluminum was cheaper. The T slots with nuts from 80/20 work great for bolting things down.
http://i228.photobucket.com/albums/ee288/earlysb1/Shop/wt1.jpg

plastikosmd
04-14-2012, 11:30 AM
my surface 'table' is a bit bigger but followed the same advice as above. It made a great welding table. Added some wheels and a ironworker, I should bolt a vise to it also....hmmm
http://i76.photobucket.com/albums/j5/plastikosmd/weldingbench.jpg

vpt
04-14-2012, 11:37 AM
This was an old welding project with surplus 80/20 t-slot purchased off ebay when aluminum was cheaper. The T slots with nuts from 80/20 work great for bolting things down.
http://i228.photobucket.com/albums/ee288/earlysb1/Shop/wt1.jpg


Thats a bit big and to open for me and probably to weak for some stuff. I like big solid chunks to bolt my stuff down to. :D

Mcgyver
04-14-2012, 01:45 PM
I don't think there's any doubt it is a surface plate, but it doesn't look like it has been used for one so I wouldn't rely on it. Nice piece of iron though....if I had to buy an 18x18 to scrape it in I'm not sure what use it would serve....as I'd already then have the 18x18! :p

with dubious existing accuracy 75 is too high imo.

donf
04-14-2012, 02:12 PM
with dubious existing accuracy 75 is too high imo.
Yes I emailed him back thanking him for the bigger pictures and telling him I'm going to look for a nicer finished plate.

toolmaker76
04-14-2012, 10:00 PM
One thing I had thought to mention is that it is cast iron- the feature of cast iron is that it does not swell with the dings the way that steel does. For the most part, stone it and it is good to go again.

That being said, it still may not be what you want in a surface plate, and I'm not sure I would be interested at that price. But there would probably be a lower price point where I would be interested and would not be afraid to use it.

At the shop where I served my apprenticeship, there were a couple of different cast iron surface plates, and each bench had a smaller cast iron surface plate, just guessing (over a span of about 30 years) 12" x 15" or so. Very handy, and if it got dinged up too bad, touch it up on the Blanchard and stone the grind marks out of it. Not granite to be sure, and not calibrated, but handy nonetheless.

J Tiers
04-14-2012, 10:24 PM
Cast iron DOES have SOME growth at the side of a ding.... if the metal isn't chipped off it has to go SOMEWHERE....

That's the nice thing about granite..... granite does not have ANY "swelling"..... it chips, or it doesn't.

An old granite flat may be worn, but dings won't hurt it. But if it is really dinged-up, it may be worn badly also....

oldtiffie
04-14-2012, 11:23 PM
If it were me and if its cost was close to zero, I'd just get a facing cut done on a Blanchard grinder and test it against a known good surface plate.

Scraping if any should be minimal.

Again, a good big shaper used as a planer should do very well too.

Fly-cutting on a big well trammed mill should do OK as well.

If nothing else it would do nicely as a marking out or setting up table.

But I bought my "float glass" table to save me all that trouble.

http://bbs.homeshopmachinist.net/showpost.php?p=492764&postcount=66

Greg Q
04-14-2012, 11:54 PM
It is no longer a surface plate. I have a similar one, and it took two days to scrape in using a biax power scraper. Getting anything touched up on a Blanchard around here costs more than a new granite plate.

The only reason that I bothered to restore mine was its application as a spotting master when restoring the horizontal ways on my universal mills.

+1 on the observation that metal plates get a raised crater rim around any dings.

Mcgyver
04-15-2012, 12:33 AM
It is no longer a surface plate. I have a similar one, and it took two days to scrape in using a biax power scraper. Getting anything touched up on a Blanchard around here costs more than a new granite plate.

+1 on the observation that metal plates get a raised crater rim around any dings.

yeah maybe less than steel, but the metal has to displace somewhere

anyone ever blanchard ground something like this? I heard of wood planes going ka-boing when ground because of the heat, but then again may be thats BS because they had to be ground at the factory.

Coolant or no, there are high local temps when grinding and that may carry a big risk on thin sections like that

oldtiffie
04-15-2012, 02:01 AM
yeah maybe less than steel, but the metal has to displace somewhere

anyone ever blanchard ground something like this? I heard of wood planes going ka-boing when ground because of the heat, but then again may be thats BS because they had to be ground at the factory.

Coolant or no, there are high local temps when grinding and that may carry a big risk on thin sections like that

I ran a Blanchard - under supervision - when I was an apprentice. Its quite spectacular when one of those wheel segments "lets go" - you don't forget it easily - and it makes you more careful of all grinders.

But uner a good operator who "knows" his machine, accidents rarely happen.

Blanchard (segmented) wheels are pretty coarse and generate quite low levels of heat as might be the case with a fine wheel on a surface grinder.

http://i200.photobucket.com/albums/aa294/oldtiffie/Precision_grinding/Surf_Grinder2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Precision_grinding/Surf_Grinder3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Precision_grinding/Surf_Grinder4.jpg


A good Blanchard grinder operator - who takes "due care" - will do that easily. 'coz there ain't too many around who were less than careful.

http://www.google.com.au/search?q=blanchard+grinder&hl=en&rlz=1W1IRFC_enAU360&biw=1920&bih=785&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=MWCKT9y4IqvEmQXo7P3YCQ&sqi=2&ved=0CEQQsAQ

http://www.google.com.au/#hl=en&sugexp=frgbld&gs_nf=1&cp=16&gs_id=1s&xhr=t&q=blanchard+grinder&pf=p&rlz=1W1IRFC_enAU360&sclient=psy-ab&oq=blanchard+grinde&aq=0&aqi=g4&aql=&gs_l=&pbx=1&fp=1&biw=1920&bih=785&cad=b&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb

John Stevenson
04-15-2012, 08:01 AM
First of all what is it going to be used for ?
Many of us have surface plate but how many use them for scraping? Chances are most use them for marking out and in that case a plate such as this is far more accurate than the MK l eyeball.

Add to this who actually scrapes parts that are 18" long.

bborr01
04-15-2012, 08:29 AM
yeah maybe less than steel, but the metal has to displace somewhere

anyone ever blanchard ground something like this? I heard of wood planes going ka-boing when ground because of the heat, but then again may be thats BS because they had to be ground at the factory.

Coolant or no, there are high local temps when grinding and that may carry a big risk on thin sections like that

I have spent a lot of time running a Blanchard Grinder (Tub). Coolant for sure on a plate like that. I never ground anything dry that I can recall.

The first time I had to grind a plate I asked one of the more experienced journeymen about blocking the plate on the chuck. I was told that there is no way a plate that large is coming off the chuck unless the magnet gets turned off. In better than 25 years of running one, I never lost a plate from the magnetic chuck.

One other thing about Blanchard grinding a plate. You need to feed fairly aggressively to keep the wheel breaking down and keep it from glazing over.

Brian

donf
04-15-2012, 12:17 PM
First of all what is it going to be used for ?
Many of us have surface plate but how many use them for scraping? Chances are most use them for marking out and in that case a plate such as this is far more accurate than the MK l eyeball.

Add to this who actually scrapes parts that are 18" long.
I'm not sure who this was directed at since the thread seems to have taken on a life of its own with many interesting tidbits of info. I definitely don't need a 18" plate, its just what happened to be for sale close by. I have been using the machined table surface of my X3 to scribe parts. I was hoping to upgrade to a surface without t slots sometime in the future. I also would like to have a flat surface to check a few parts on my imported lathe. Its OK, but the compound side is awful! Its either too tight or too loose. I found a 8x section http://yoshiokasyd.web.fc2.com/Annexes/Machine_Tools/Lathe/slide_lapping/slide_lapping.htm and it seems this person had the same problem and was able to make it a bit better. I know it doesn't mention a surface plate on the page, but I was thinking a flat surface might be the place to start before touching anything.

Rosco-P
04-15-2012, 12:59 PM
18x18 too big? Don't agree with that, but $75 for a plate that size that needs work is a bit much. To renew the surface, I'd find someone with a planer, not a grinder, the finish would be better and the bill for the work less. You might even find a "hobbyist/collector" with a suitable sized planer or shaper.
It's been pointed out before, a machine table, a chunk of glass or a sink cutout from a granite counter is not a surface plate. If I'm seeking that level of accuracy, I'd use the cast iron top of my Delta Unisaw for layout/inspection.

Forrest Addy
04-15-2012, 03:16 PM
Lets say you have an opportunity if you acquire that surface plate. I just thought of a metaphor to put the enterprize in perspective: Owning a cast iron surface plate is like owning an 80 year old gaff rigged sloop, a wood sailboat with galvanized fittings and canvas sails. Both are old, highly esteemed by those in the know, revered by those not in the know but love the stories, go for cheap, require - absolutely require - regular maintenence and extra care when using it for the purpose for which it was intended. Do all these things right and the cast iron surface plate (and the wood sailboat) will serve you well for a long time. But you absolutely positively have to maintain them.

That surface plate is about 20 hours of hand scraping from being as accurate as when new. But to hand scrape it you need to learn the ropes and acqure some basic tools among these a granite surface plate about the same size as the cast iron one.

But that's where we came in isn't it? Buy a granite surface plate that's superior to cast iron in every attribute but weight and just use it to fix a cast iron one. Oh, the Irony! (Or is it masonry?) Here's where you ask yourself do I have the persistance, patience, and the desire to own and maintain a cast iron surface plate (wood sailboat)?

As for a simple "grind the cast iron to clean up" and let it go at that is a bit like beaching the sailboat and moving aboard. The ground surface will be about as satisfactory in machine shop precision as an immobilized sailboat is to navigation. I'm sure Old Tiffie will write a long detailed rebuttal for this assertion but the difference between a ground surface or a piece of float glass to a good surface plate in a machine shop is too vast apparently to comprehend in some quarters. I wish I could afford the send him a good suface plate if only to reduce HSM's bandwidth.

But there's is a difference in scale: The cast iron surface plate will take 20 hours to recondition and a couple hundred dollars in tools you can use elsewhere. A 32 ft wood sailboat can take a coupe of years 6000 hours and $40,000 to restore to seaworthy condition. Add $5000 ro recondition the auxilliary and another $30,000 for spars, fitments, furnishings, habitability, paint and sandpaper, rigging, sails, instrumnts, navigation, and radio equipment, hauling and docking, and outfiting. That's if you do about half the work yourself.

Personally much as I love salty old sailboats I'll take the cast iron surface plate.

donf
04-15-2012, 04:33 PM
Someone must have felt the same way... it sold really fast after I posted it here! Either that or its now a welding table! :)

John Stevenson
04-15-2012, 04:53 PM
I wish I could afford the send him a good suface plate if only to reduce HSM's bandwidth.



Just send him a picture, that's all he needs :D

Rosco-P
04-15-2012, 06:30 PM
As for a simple "grind the cast iron to clean up" and let it go at that is a bit like beaching the sailboat and moving aboard. The ground surface will be about as satisfactory in machine shop precision as an immobilized sailboat is to navigation.

For a CI suface plate that has seen some abuse, deep scratches, nicks, peen marks, would planing the surface to clean it up, prior to scraping it flat be the proper approach?

J Tiers
04-15-2012, 06:54 PM
First of all what is it going to be used for ?
Many of us have surface plate but how many use them for scraping? Chances are most use them for marking out and in that case a plate such as this is far more accurate than the MK l eyeball.

Add to this who actually scrapes parts that are 18" long.

Good points. Marking out is probably good to 0.25mm, average, and that much wear is a lot, unless the thing was used for lapping.

As for who, me for one.... I am trying to scam a 36" (at least 24") straightedge at the moment, for lathe bed scraping.... Might have to scrape my own, in which case I would need access to a largeish plate from 24 inch to metre long as a standard. (wouldn't need to be very wide, if long enough).

I had a line on a 24" SE, but no go now.... Might have to scrape a 24" CI level, but I have doubts about its stability.

John Stevenson
04-15-2012, 07:29 PM
The ground surface will be about as satisfactory in machine shop precision as an immobilized sailboat is to navigation.

Sorry but I don't agree with this statement.
It seems we have two schools of thought, the old timers who say it has to be planed then hand scraped to flat and the more modern school that says ground, then possibly followed on by hand scraping.

Planing is going to be flat but have troughs on from the planing tool. Grinding is going to be flat with tool marks from the grinding process but no troughs.

Grinding can easily get to 4 Um and as close as 2Um, planing can get nowhere near this.

If scraping is the ultimate surface then why are linear rails not scraped or bearing tracks?

Why do they have to resort to grinding ?

Look at any modern mass produced machine tools, capable of working to far greater tolerances than any previous machines before and not one scraped surface in sight.

Rosco-P
04-15-2012, 07:34 PM
But isn't that what these boys are doing? http://www.youtube.com/watch?v=UdDDe9oqZ4E

John Stevenson
04-15-2012, 07:42 PM
Rosco,
I stand corrected, not seen that video before and I was going on the ones I have seen like DMG, Haas and similar.

Rosco-P
04-15-2012, 07:48 PM
Rosco,
I stand corrected, not seen that video before and I was going on the ones I have seen like DMG, Haas and similar.

Ran across that vid while looking at Mueller Nick's(?) scraping videos. Certainly not the standard procedure for most machine builders. Printing press beds used to be scraped flat.

Forrest Addy
04-15-2012, 08:06 PM
Sorry but I don't agree with this statement.
It seems we have two schools of thought, the old timers who say it has to be planed then hand scraped to flat and the more modern school that says ground, then possibly followed on by hand scraping.

Planing is going to be flat but have troughs on from the planing tool. Grinding is going to be flat with tool marks from the grinding process but no troughs.

Grinding can easily get to 4 Um and as close as 2Um, planing can get nowhere near this.

If scraping is the ultimate surface then why are linear rails not scraped or bearing tracks?

Why do they have to resort to grinding ?

Look at any modern mass produced machine tools, capable of working to far greater tolerances than any previous machines before and not one scraped surface in sight.

Sorry, I don't agree except to concur most any non-injurious machining methods is a good prep for precision scraping.

Here's where I disagree: I'm an old planer hand. I've prep-planed many a machine tool carcass to finish and lineraity and alignment achieving preliminatry fit-ups between mating parts and made them ready for scraping. Planing in this sense is 4 to 10 times as productive as scraping to the same stage of fit and alignment depending on the stock to be removed. Scraping in this context serves to enhance fit, correct alignment, and develop the bearing.

Planing machine tool way surfaces uses a technique called "broadnosing" where a wide gooseneck tool is precision ground on the edge, set paallel to the surface to be cut to close tolerance, incrementally fed about 3/4 the tool width (a 1" wide tool wasn't uncommon when working to larger scales). In the final cuts the edge was refreshed, the depth of cut was reduced to 0.001' or less and the tool parallelism was set to 0.0001" or close as you can get it. The planed surface was for all practical purposes scraped flat as the planer's geometry allowed. Lay a sheet of paper on the planes surface and rub it with a pencil lead. No feed marks, none. The surface at this stage looks like parallel ribbons of gray satin.

I used to work with an old scraper hand. He was so quick and efficient I could never keep up with him but I supported his scraping with inspired planer prep. We once took the major castings for a #3 Mulwaukee from worn out to scraped and ready to assemble in about 8 days.

So careful. Sir John (at this point you should be backing away respectfully tugging your forelock) when you slight planers and the feed marks they leave behind. I'm an old planer hand and as such I'm a delicate flower.

oldtiffie
04-15-2012, 08:22 PM
Here is the OP:
This popped up used - its supposed to be an old 18x18 calibrated surface plate with legs, but look at the big dings! They are asking $75, but after I saw the dings in the picture I am thinking a 12x12 granite one from shars for about the same price shipped is looking pretty good! I have very little machine tool knowledge so I just figured I would get a second opinion in case I was over looking something.
There are degrees of "flat(ness)" from say the the plate the OP was thinking of buying through to machine tables, float glass and surface plates (Grades AA, A and B).

Its simply a matter of knowing just how much "flatness" you need for a particular job - and getting and using it.

Scraping a surface plate has been mentioned frequently but the flatness and quality of the surface has not.

The OP's plate (18" x 18") - 457mm x 457mm - "rounded" to 450mm x 450mm (as the USA specs are metric now).

http://www.tru-stone.com/pdf/FedSpecGGG-P-463c%20amendment%201.pdf

Now looking at page 4, the limits in micrometers (um) for 450 x 450 plates total flatness tolererance are:

AA: 1.6um (x 0.00004" = 0.000064" ~ 0.64 "tenths")

A: 3.3um (x 0.00004" = 0.00013" ~ 1.3 "tenths")

B: 6.6um (x 0.0004" = 0.00026" ~ 2.6 "tenths")

So decide on what class of flatness you want that surface plate to be.

The plate you are scraping to (the referenes) should be at least equal to and not less than the plate you are scraping so you would ness a Class B "reference" to scrape a plate to Class "B".

Ideally the reference plate should be one Grade above the plate being scraped - a reference plate should be Grade AA to scrape a Grade A plate.

But that said, you are limited by the Grade of the reference plate you have (which should have been calibrated - just to be sure - as a non-claibrated plate may well be a "B").

So far I have only considered 2 x 450 square plates but ideally (and practically) the next size up reference plate (600mm x 600mm) aka 24" x 24" should be used so that the plate being scraped (450 sq) fits wholly within the reference plate (600sq).

But the flatness limits for 600mm square plates are:
AA: 2.2um (0.000088" ~ 0.88 "tenths")

A: 4.4um (0.000176" ~ 1.76 "tenths")

B: 8.6um (0.000344" ~ 3.44 "tenths)

So a Grade A 450 (3.3um) plate to be scraped will need a 600mm Grade AA (2.2um) sq reference plate.

A Grade B 450 (6.6um) plate will need a 600mm Grade A (4.4um) reference plate.

Scraping a smaller plate to an overly large reference plate is not always a good idea.

If a plate is scraped to another with no known Grade, the best that can be said of the plate being scraped is the it may be equal to but not better than the plate with the unknown Grade.

Same applies to the "3-plate" system of scraping 3 plates to all be "blue-d" equally when all are finally scraped to each other and checked. They may all be flat, but how falt is a matter of judgement/assessment which may be purely subjective (no measurements) as "Grading" a scraped plate required definitive measurement (objectivity) or comparison to a known classified reference plate.

(This is ignoring precision level and electronic measurement and classification).

So this scraping stuff is not always as basic or easy as it seems.

Again, only get or scrape a surface to the accuracy required of the job's it is to be used for.

Grade B (workshop and test) plates have been used very satisfactorily in syhops, tool rooms and metrology for years.

Hence my use of float glass and machine tables for most day-to-day work.

Same with my Class B slip guages as there are plenty of other adequate known sizes to be used in the shop.


Gauge blocks are available in various grades, depending on their intended use.[6] The grading criterion is tightness of tolerance on their sizes; thus higher grades are made to tighter tolerances and have higher accuracy and precision. Various grading standards include: JIS B 7506-1997 (Japan)/DIN 861-1980 (Germany), ASME (US), BS 4311: Part 1: 1993 (UK). Tolerances will vary within the same grade as the thickness of the material increases.
reference (AAA): small tolerance (0.05 μm or 0.000002 in) used to establish standards
calibration (AA): (tolerance +0.10 μm to −0.05 μm) used to calibrate inspection blocks and very high precision gauging
inspection (A): (tolerance +0.15 μm to −0.05 μm) used as toolroom standards for setting other gauging tools
workshop (B): large tolerance (tolerance +0.25 μm to −0.15 μm) used as shop standards for precision measurement

More recent grade designations include (U.S. Federal Specification GGG-G-15C):
0.5 — generally equivalent to grade AAA
1 — generally equivalent to grade AA
2 — generally equivalent to grade A+
3 — compromise grade between A and B

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

John Stevenson
04-16-2012, 02:41 AM
So careful. Sir John (at this point you should be backing away respectfully tugging your forelock) when you slight planers and the feed marks they leave behind. I'm an old planer hand and as such I'm a delicate flower.

Forrest,
With all due respect I'm not slighting planers and what went before but where are they today ?
This week in the UK is MACH 2012, one of the biggest machine tool shows we have every two years.
Not one planer in sight.

now granted that the UK isn't the most productive country in making Machine tools but what is on show is from manufacturers from all round the world.

Year before last year I was over in Shanghai, at whatever they call thier show, anyway big, 20 times the size of the UK show.

Guess what, no planers.

So how come given modern costings and production methods some one hasn't resurrected the planer ? Or why did it die in the first place ?

Answers on the back of a current Haas, Mori Seki, DMG, brochure on current shaping machines.

Sorry Forrest the world has moved on.

The Artful Bodger
04-16-2012, 02:58 AM
You can have a new planer sent to you 60 days after order...

http://haven-equipment.en.made-in-china.com/product/LoYQORsUnSrw/China-Planing-Machine-Gantry-Planer-BQ20A-C-Serials.html

oldtiffie
04-16-2012, 03:01 AM
I agree with John S.

I'd prefer a ground surface any day - preferably with an overlapping "swirl" as you'd get with a vertical spindle grinder (Blanchard etc.) - for lubrication.

Just run a good oil stone over with kerosene (here and UK parrafin USA) to get rid of the burrs and you'd be pretty well on your way - follow-up scraping is optional.

If its smooth and dry when you run your open hand over it its pretty good.

But as advised previously, a blanchard grind (here in OZ) costs more than a new granite plate of the same size - your choice of Grade (AA, A, B).

So cost, time and effort wise its a no-brainer - either leave it where it is or at the scrappers or "bin" it.

Dr Stan
04-16-2012, 03:06 AM
You can have a new planer sent to you 60 days after order...

http://haven-equipment.en.made-in-china.com/product/LoYQORsUnSrw/China-Planing-Machine-Gantry-Planer-BQ20A-C-Serials.html

Interesting, figured they were only available on the used market like the one I have, a 1900 or so Cincinnati with a 9' bed.

John Stevenson
04-16-2012, 03:07 AM
You can have a new planer sent to you 60 days after order...

http://haven-equipment.en.made-in-china.com/product/LoYQORsUnSrw/China-Planing-Machine-Gantry-Planer-BQ20A-C-Serials.html

Doesn't mean to say they make them, only advertise them. They don't even have a picture only a computer graphic.

I'm not the only guy who goes to shows, has anyone else seen a new planer in the last 10 years ?
Seen more big grinders and slideway grinders than you can shake a stick at but no planers, they must be hiding ?

The Artful Bodger
04-16-2012, 04:01 AM
Doesn't mean to say they make them, only advertise them. They don't even have a picture only a computer graphic.



Call their bluff, put an order in!:D

.RC.
04-16-2012, 04:29 AM
But the flatness limits for 600mm square plates are:


You need to find out what this device is for..

http://www.rochestermachinerysuppliers.com/display_machine.asp?id=284

oldtiffie
04-16-2012, 06:15 AM
I and at least several others here know what it is and what it does and is used for, but as the chances of anyone here with the exception of a very few either having one or intending to buy one, the chances of most of us here ever getting our plates checked and Graded on one locally are that close to zero - particularly when they buy them is sweet FA - that it doesn't matter.

Those that have them tested will have to hope the results are OK first up as if they are not they have quite an enigma on their hands - to leave the plate as not graded or have the plate re-lapped and re-tested and re-graded all of which may well cost a lot more than a new Graded plate.

That's really in the nice to know but not in the need to know category.

Greg Q
04-16-2012, 06:51 AM
Good luck finding anyone down here who will lap a plate into certified accuracy. When I checked on calibration only prices down here I was quoted three hours (including travel) and $600. No lapping available, and they are the biggest cal lab in town.

There are limits and there are limits. Moore Special Tools celebrated accuracy was built on reference tools they scraped in-house to twenty millionths. Which you locate on any spec sheets anywhere.

whitis
04-16-2012, 07:33 AM
How it's made, season 1, episode 14 (netflix streaming) shows the process of quarrying, sawing, polishing, and flaming granite slabs. Not to surface plate accuracy. Before that, it shows grinding and machining eyeglass lenses.

.RC.
04-16-2012, 07:34 AM
I and at least several others here know what it is and what it does and is used for,

whooooooosh I see my post went straight over your head....

When you go and understand what repeatability is, you will know why your post about not being able to scrape a small plate on a bigger plate to the same grade is just plain not true...


But given we had this identical discussion about 14 months ago on this same forum with the same spec sheets posted I doubt anything will change.... You cannot teach an old dog new tricks...

oldtiffie
04-16-2012, 07:46 AM
Thanks Greg.

Could not find Moore Special tools - link please.

Hand scraping to 40 millionths (micro-inches) is really really very good but in metric terms is 1 micrometre (um). That I presume will be 1 um between limits (high and low). How big was that plate?

I take it that the short answer if you can't but need to (re) assure yourself of the calibration of your plate (ie its Grade - AA, A, or B) you might as well toss it in the bin and buy a new calibrated one to your required Grade.

Or alternatively if the vendor cannot provide you with the calibration and Grade you might as well regard it as suspect at best and out of calibration at worst and just not buy it.

I deliberately bought my 630sq granite plate and my granite square from MTI Qualos (Melbourne) and was only too pleased to pay a premium price for premium products.

http://www.mtiqualos.com.au/

at:

http://www.google.com.au/#hl=en&rlz=1W1IRFC_enAU360&sclient=psy-ab&q=mti+qualos&rlz=1W1IRFC_enAU360&oq=mti&aq=1&aqi=g4&aql=&gs_l=hp.1.1.0l4.0l0l1l269l0l0l0l0l0l0l0l0ll0l0.frg bld.&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=7e4ff99727deda82&biw=1280&bih=523

oldtiffie
04-16-2012, 07:56 AM
Originally Posted by oldtiffie

I and at least several others here know what it is and what it does and is used for,


whooooooosh I see my post went straight over your head....

When you go and understand what repeatability is, you will know why your post about not being able to scrape a small plate on a bigger plate to the same grade is just plain not true...


But given we had this identical discussion about 14 months ago on this same forum with the same spec sheets posted I doubt anything will change.... You cannot teach an old dog new tricks...

Not so.

See page 3 Table 11 (Metric) "Tolerances for repeat measurement of readings" (Full Indicator Movement (um))

http://www.tru-stone.com/pdf/FedSpecGGG-P-463c%20amendment%201.pdf

.RC.
04-16-2012, 08:15 AM
You do not know what repeatability means...

Mcgyver
04-16-2012, 08:38 AM
You do not know what repeatability means...


least not the variety you're referring to :D

Greg Q
04-16-2012, 09:10 AM
Re: Moore Special Tools: i have no link, instead alluding to their fine book "Foundations of Mechanical Accuracy", and failing that, a like named chapter in their earlier book "Holes, Surfaces and Contours"

"Foundations" is still in print at text book price$, "Holes" appears on ebay from time to time.

Moore is perhaps less well known here than the Swiss companies, but they made some damned fine machines including their ubiquitous jig bores. Machines that embodied/defined the limits of physical accuracy in an era when it really mattered. They day after Kruschev banged his crappy shoe on the UN podium I'll bet that Moore's phone was ringing off the hook. Ditto when JFK pointed to the moon. Etc etc. since I am a child of that place and time I plan to add a nice Moore 1 1/2 jig bore to my shop once I settle down.

Greg

John Stevenson
04-16-2012, 10:30 AM
Thanks Greg.

Could not find Moore Special tools - link please.



Tiffiepedia failed again ? :D

Forrest Addy
04-16-2012, 11:08 AM
Forrest,
With all due respect I'm not slighting planers and what went before but where are they today ?
This week in the UK is MACH 2012, one of the biggest machine tool shows we have every two years.
Not one planer in sight.

now granted that the UK isn't the most productive country in making Machine tools but what is on show is from manufacturers from all round the world.

Year before last year I was over in Shanghai, at whatever they call thier show, anyway big, 20 times the size of the UK show.

Guess what, no planers.

So how come given modern costings and production methods some one hasn't resurrected the planer ? Or why did it die in the first place ?

Answers on the back of a current Haas, Mori Seki, DMG, brochure on current shaping machines.

Sorry Forrest the world has moved on.

You're right on. Planers are obsolete, They're big, unproductive, take up acres of floor space and the few things they do exceedingly well can be done with more productive machines almost as well. If I had a shop there would be a planer in it only to support machine tool re-conditioning or making press brake dies. If such work seldom appeared on my horizon I'd get rid of it and use the 16 z 40 (or 60 or 80) foot floor space for a string of CNC machines to make me 10X the money per unit of floor.

Which brings us to another point: scraping is an obsolete skill now reduced to niche status. There are machine tools \that develop accurate finishes flatter than a scraper can produce in a far shorter time. However these machines are large and expensive and time on them is costly. Work has to be fetched to them and few machine tool components are had portable. A scraper's full array of tools and equipment will fit in a medium sized JobBox. Scraping references may be bulky and heavy in the larger sizes but their shipping is a fraction of a machine tool's structural elements.

So whether to grind or scrape is a more complex question than a mere partizan arguement can resolve. The first point is what work needs to be done and what assets are immediately available. If the work is to recondition a conventional machine tool to new machine accuracy and longevity and a good scraper hand and a planer is available then that is the way to go. If the scraper hand is not available and a machine tool rebuilder across town has a way grinder then... and so on acroiss a wide spectrum of alternatives, funding, and available resources with retrofitting complicating the picture.

My point is a home shop machinist, should he wish to develop the skills and acquire the tools, can rebuild older technology machine tools in his home shop and his only investment beyond his basic tools is his own labor. The presence of way grinders etc and rebuild services don't negate a home shop guy's on-site efforts You fellows who point out your preferred alternative as though the general issue is resolved forever need to walk a mile in the other guys moccasins. A single chang in circumstances and available resources inevitably alters the best solution to a given problem.

JCHannum
04-16-2012, 11:17 AM
"Foundations" is still in print at text book price$, "Holes" appears on ebay from time to time.

Both books are currently available from Moore. Prices are not for the faint of heart, but both are excellent references for anyone interested in what is required to achieve true accuracy;

http://www.mooretool.com/publications.html

oldtiffie
04-16-2012, 07:50 PM
You do not know what repeatability means...

Try this for localised testing

http://www.starrett.com/metrology/metrology-products/precision-granite/calibration-products/repeat-reading-gage

See page 3/16:
http://www.starrett.com/docs/data-sheets/tru-stone---bulletin-807.pdf?Status=Master

Anything else you'd like me to find for you?

I can't see how it affects scraping on a plate - either the job or the plate.

John Stevenson
04-16-2012, 08:10 PM
Don't tell us, show us something you have scraped.

Mcgyver
04-16-2012, 09:45 PM
Don't tell us, show us something you have scraped.

that reminds me of that to horrible creature too many tools or something like that? now there was wanker!

the least these guys could do is bring some humour with it and character damn it!....I mean who didn't tune in when Airsmith was firing on all brain cells, and Millman, now there was a guy you could really take some grumpy lesson from. classic stuff. This new breed of trolls, i dunno, its like bad pop music, lots of noise but its missing the hook

:D
:D
:D

Greg Q
04-16-2012, 10:08 PM
that reminds me of that to horrible creature too many tools or something like that? now there was wanker!

the least these guys could do is bring some humour with it and character damn it!....I mean who didn't tune in when Airsmith was firing on all brain cells, and Millman, now there was a guy you could really take some grumpy lesson from. classic stuff. This new breed of trolls, i dunno, its like bad pop music, lots of noise but its missing the hook

:D
:D
:D
What ever happened to Airsmith? I had him on my ignore list to prevent my own brain cell suicide, then I see that he is now mentioned in the past tense. Still, I have more ignored guys on PM than here now.

Back to the topic at hand:

Git (slang)
From Wikipedia, the free encyclopedia

Git is mild profanity with origins in British English for a silly, incompetent, stupid, annoying, senile elderly or childish person.[2] It is usually an insult, more severe than twit or idiot but less severe than wanker, arsehole or twat.

.RC.
04-16-2012, 10:18 PM
I can't see how it affects scraping on a plate - either the job or the plate.

Well I will tell you....

Repeatability is important as while a plate may be in spec for flatness it cannot have a mountain anywhere on it that takes up the whole tolerance at one point

Any error of flatness has to be gradual not abrupt.. That is why you were in error saying you cannot use a large A plate to scrape a small A plate..

You can because any error on the large plate if within spec is gradual error, not all contained within one small region...

The two requirements of flatness and repeatability complement one another and you cannot go on about one while ignoring the other...

Some very smart people sorted all that out many years ago..

J Tiers
04-16-2012, 10:26 PM
Repeatability is important as while a plate may be in spec for flatness it cannot have a mountain anywhere on it that takes up the whole tolerance at one point



That surely messes up the "spin" test, doesn't it?.....;)

Greg Q
04-16-2012, 10:33 PM
In fact it does somewhat. When I scraped one of my masters it liked to wring to the plate with just the slightest bit of lube from the thinnest smear of spotting dye.

The 18" square cast plate would take some effort to pry from the granite...although I use "pry" in the poetic sense, it was still disquieting to have to slide it off the granite to break the bond.

Greg

Forrest Addy
04-16-2012, 10:53 PM
Tiffie, Leaping to conclusions? You should know that a Repeat-o-Meter while a great instrument will tes only for sphericity. If the instrument happens to have been zero-set on a sphere of infinite radius then it will indeed test for localised departures from flatness down to the sensitivity of the dial indicator/LDVT installed in it.

If this instrument is used with a pair of level heads connected to a differential gage amplifier then the combination will calibrate a flat surfece to 0.5 arc seconds - roughy a slope of 1/400,000 or 30 millionths per ft. The leveing heads will detect overall errors while the Repeat-o-Meter will detact localised errors like humps, dips, and edge roll-off.

There are other ways of checking flatness of a surface plate like with an optical columator, testing agains a straight edge of known and tabulated error, optical interferometry, and about a dozen other methods most very equipment intensive.

The Repeat-o-Meter and the differential level is about the least expensive save one: a master precision level but the surface being checked has to be set up absolutely rigid otherwise the weight of the level will purturb the level indications resulting in false readings. By rigid I mean setting up with steel wedges on solid masonry. A milling machine table or a lathe bed will likely have too much flex unless the machine is stout and the base is grouted to the floor.

All readings collected will have to be verified by level reversal and taken repeatedly over a period of several days. You will be reading a 0.0005" in 10" sensitivity level to 0.0001" per ft. This is beyond the specified sensitivity of the instrument but if sufficient care is taken you can take reliable repeatable readings and determine flatness and locate areas of wear on a surface plate to 0.0001" per ft.

OTH you can buy a new import surface plate (here in the US) for less thn $100 and junk the one you have.

BTW defunct largish surface plates are god-sends to candymakers and bakers who need a large cool surface on which to work their magic.

mike4
04-16-2012, 11:33 PM
18x18 too big? Don't agree with that, but $75 for a plate that size that needs work is a bit much. To renew the surface, I'd find someone with a planer, not a grinder, the finish would be better and the bill for the work less. You might even find a "hobbyist/collector" with a suitable sized planer or shaper.
It's been pointed out before, a machine table, a chunk of glass or a sink cutout from a granite counter is not a surface plate. If I'm seeking that level of accuracy, I'd use the cast iron top of my Delta Unisaw for layout/inspection.

I have noted that many are knocking the flatness of glass in particular Float glass , and I see in the post above that the table of a machine is not accurate either .
I am curious as to what level of "flat " is required .
I am not wanting to start a fire or pissing contest just want to know how flat some items are and if so why they can or cannot be used for setup .

I have seem some very optocally flat glass in university laser labs which would make most surface plates look like the lunar surface.
Michael

J Tiers
04-16-2012, 11:47 PM
Flat means to 0.0001 or so, max, preferably less, for scraping or precision reference purposes....

Flat also has the connotation of "solid and rigid" enough not to bend and become un-flat when things are put on it for testing. That tends to mean thick, which float glass usually is not.

There WERE glass surface plates made during WW2, to save cast iron. Someone had one that they were considering buying, I don't recall which forum the discussion was on, maybe here, maybe Chaski. Was from Cadillac Gage, IIRC.

If you want to do layout, glass, or a chunk of granite countertop may be perfect. Tolerances are what they are, and the "punishment should fit the crime" so to speak, depending on what you need to do.

.RC.
04-17-2012, 12:00 AM
I have noted that many are knocking the flatness of glass in particular Float glass , and I see in the post above that the table of a machine is not accurate either .
I am curious as to what level of "flat " is required .
I am not wanting to start a fire or pissing contest just want to know how flat some items are and if so why they can or cannot be used for setup .

I have seem some very optocally flat glass in university laser labs which would make most surface plates look like the lunar surface.
Michael

I think the biggest concern with glass is it is not stiff enough in the sections we normally see...

Put it on a curved surface and it will bend to that curvature...

I have seen one image of a glass surface plate, and it must have been 3 inches thick and only 12 inches across...

Forrest Addy
04-17-2012, 12:15 AM
I'm with Jerry n this. Glass is not a magical material. It has physical properties just as any other material. Gglass has about 1/4 the stiffness of an equivalent steel plate. I'm aware that different breeds of glass have different Young's moduli so don't roast me on this.

Cast iron surface plates are elaborately ribbed on the back side for rigidity and granite plates are made thick; thicker for the higher accuracy cert. Ive seen 4 ft x 8 ft grainte surface plates 20" thick.

A piece of 1/4" glass may start out fairly flat when in the free state but place it on a bench and place about 10 lb of work, V block and transfer gage on it s and the glass will sag just like any other material.

If you need a good layout surface use a machine table or the table saw top. Glass's reputation as a flat working surface and lapping plate is a cruel joke that noobs and shade-tree yokels fail to accept when challenged by knowledgeable suthority..

oldtiffie
04-17-2012, 12:28 AM
Originally Posted by oldtiffie


I can't see how it affects scraping on a plate - either the job or the plate.


Well I will tell you....

Repeatability is important as while a plate may be in spec for flatness it cannot have a mountain anywhere on it that takes up the whole tolerance at one point

Any error of flatness has to be gradual not abrupt.. That is why you were in error saying you cannot use a large A plate to scrape a small A plate..

You can because any error on the large plate if within spec is gradual error, not all contained within one small region...

The two requirements of flatness and repeatability complement one another and you cannot go on about one while ignoring the other...

Some very smart people sorted all that out many years ago..

If or as all newly calibrated plates conform to the US standard - as do Starrett - so that all "comply", it is implicit that they by definition will include compliance as regards "Repeat Measurements" etc.

See page 3 Table 11 (Metric) "Tolerances for repeat measurement of readings" (Full Indicator Movement (um))

at:

http://www.tru-stone.com/pdf/FedSpecGGG-P-463c%20amendment%201.pdf

So, it is taken care of in new plates during manufacture.

If such a problem should arise in a plate that is being scraped to a correct plate and if/as it will be in the plate being scraped it is a problem for the person doing the scraping.

Before anyone gets too carried aaway, I suggest that they read "page 3 Table 11 (Metric) "Tolerances for repeat measurement of readings" (Full Indicator Movement (um))" as you will see that for a diagonal or diameter range up to 800mm the tolerances (in um) are:

Grade AA: 0.9um (0.000036")

Grade A: 1.5um (0.00006")

Grade B: 2.8um (0.00011")


for a diagonal or diameter range up to 800mm to 1500mm the tolerances (in um) are:

Grade AA: 1.2um (0.000048")

Grade A: 1.8um ( 000072")

Grade B: 3.0um (0.00012")

Noting that these all apply to calibrated plates which are within their flatness tolerance for theit size and Grade/s and that the largest repeat measurement of readings (3.0um ~ 0.00012") is on a 1500mm (~ 59") Grade B plate it should not be a problem.

I doubt that most scrapers would either pick it up on a scraped plate or be concerned about it.

So the perceived "problem" is not a problem at all as it has been incorporated in the calibration and grading of all "complying" plates.

oldtiffie
04-17-2012, 12:41 AM
Flat means to 0.0001 or so, max, preferably less, for scraping or precision reference purposes....

Flat also has the connotation of "solid and rigid" enough not to bend and become un-flat when things are put on it for testing. That tends to mean thick, which float glass usually is not.

There WERE glass surface plates made during WW2, to save cast iron. Someone had one that they were considering buying, I don't recall which forum the discussion was on, maybe here, maybe Chaski. Was from Cadillac Gage, IIRC.

If you want to do layout, glass, or a chunk of granite countertop may be perfect. Tolerances are what they are, and the "punishment should fit the crime" so to speak, depending on what you need to do.

I think that my mill and grinder tables would go very close to the "0.0001" test and are certainly good enough for marking out and setting up.

Some are being a bit disingenous as regards the float glass as my float glass plate is used for marking out and setting out and is supported on masking tape strips at 100mm centres accross the mill table. So it is well supported on many points and is not likely to bend/deflect to any significant amount (say less than 1um ~0.00004").

I have been very careful to state that these "plates" are for setting up and marking out only - not as "surface" plates. Some seem to have taken the liberty of "reading in" something I quite explicity and deliberately did not say.

I keep my Grade AA plates to work that requires that order of accuracy - the rest goes on my other "plates" as I try to match the flatness required with the plate that meets that need.

Forrest Addy
04-17-2012, 12:49 AM
Tiffie I have never seen more eggregious examples of scholarship without contributing to understanding as your contributions to this thread. What is it you are trying to achieve? Dominance of the discourse, assert knowledge, obfuscation via hairsplitting.. I cant figure it out.

I used to work with a guy who described this level of nitpicking as "picking fly$hit out of the pepper."

You cite the US Federal Spec on surface plates GGG-P463. There complemenray ISO standard and probably many other preceding standrds evolved over the years world wide. These standard are written so little interpretation is necessary. All points you have so far brought up so far have been trivial. Let it go.

oldtiffie
04-17-2012, 12:54 AM
I'm with Jerry n this. Glass is not a magical material. It has physical properties just as any other material. Gglass has about 1/4 the stiffness of an equivalent steel plate. I'm aware that different breeds of glass have different Young's moduli so don't roast me on this.

Cast iron surface plates are elaborately ribbed on the back side for rigidity and granite plates are made thick; thicker for the higher accuracy cert. Ive seen 4 ft x 8 ft grainte surface plates 20" thick.

A piece of 1/4" glass may start out fairly flat when in the free state but place it on a bench and place about 10 lb of work, V block and transfer gage on it s and the glass will sag just like any other material.

If you need a good layout surface use a machine table or the table saw top. Glass's reputation as a flat working surface and lapping plate is a cruel joke that noobs and shade-tree yokels fail to accept when challenged by knowledgeable suthority..

Forrest,

you are being a bit disengenuous here as my glass plate is 1/2" thick "float" toughened "safety" glass and is supported at 100mm centres on masking tape accross my mill table - as you've seen (more than?) often enough. So it is fully supported.

To remind you and for your edification here it is - again - being used for setting up and marking out with a digital height gauge, a 2-3-4 block, a 0.01mm (~0.0004") dial indicator, a surface guage and a metric ruler - hardly "surface plate work". But it works very well never the less.

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Surfaceguage1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Surfaceguage3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Surfaceguage4.jpg

oldtiffie
04-17-2012, 12:59 AM
Originally Posted by mike4

I have noted that many are knocking the flatness of glass in particular Float glass , and I see in the post above that the table of a machine is not accurate either .
I am curious as to what level of "flat " is required .
I am not wanting to start a fire or pissing contest just want to know how flat some items are and if so why they can or cannot be used for setup .

I have seem some very optocally flat glass in university laser labs which would make most surface plates look like the lunar surface.
Michael


I think the biggest concern with glass is it is not stiff enough in the sections we normally see...

Put it on a curved surface and it will bend to that curvature...

I have seen one image of a glass surface plate, and it must have been 3 inches thick and only 12 inches across...

.RC.

See my previous reply to Forrest and others that my glass plate is used fully supported on my mill table specifically for setting up and marking out purposes and NOT (repeat) NOT as a surface plate.

Forrest Addy
04-17-2012, 01:40 AM
.RC.

See my previous reply to Forrest and others that my glass plate is used fully supported on my mill table specifically for setting up and marking out purposes and NOT (repeat) NOT as a surface plate.


Til you break it.

Void
04-17-2012, 01:55 AM
oldtiffie,

From your pictures: First two with the dial indicators... that is the sort of work I would use a surface plate for. Checking straightness, flatness, parallelness, etc... no layout going on there.
Last pic with the scratch gage... now that looks like it might have something to do with layout.
Not sure what the sharpening stone is doing on there. Were you dressing down the burrs on your glass?:confused:
Personally, I would never put a sharpening stone on a "precision" surface with other precision surfaces on there all at the same time. Certainly on a cleared mill table or fixture to dress down burrs and high spots, then remove it and clean away any grit before anything else touches that surface.

That glass plate with all the stuff on it is just about as flat as your mill table. So would a 1/4" thick plate of glass or even a 1/8" thick one.

The layout could be done on a bandsaw or tablesaw table with equivalent accuracy without having to clear off the mill table. Mine usually has a vise or dividing head in the middle of it. But if that is your only flat surface then you could eliminate the glass altogether and get just as good results for layout work.

I fail to see from your pictures or words how the glass plate helps at all with layout work. In my opinion it looks like a completely superfluous waste of time and valuable machine table area.

Did I miss something.

-DU-

oldtiffie
04-17-2012, 02:25 AM
oldtiffie,

From your pictures: First two with the dial indicators... that is the sort of work I would use a surface plate for. Checking straightness, flatness, parallelness, etc... no layout going on there.


I've checked that glass plate with the straight edges on my granite square as well as my cylinder squares - it came up/out very well.


Last pic with the scratch gage... now that looks like it might have something to do with layout.


It seems we agree on that.

Not sure what the sharpening stone is doing on there. Were you dressing down the burrs on your glass?:confused:


Nope - I used it to take out any6 "dings" or burrs from the mill table.


Personally, I would never put a sharpening stone on a "precision" surface with other precision surfaces on there all at the same time.


It was there as a "demo" to make a point.


Certainly on a cleared mill table or fixture to dress down burrs and high spots, then remove it and clean away any grit before anything else touches that surface.


See previous.


That glass plate with all the stuff on it is just about as flat as your mill table. So would a 1/4" thick plate of glass or even a 1/8" thick one.


True - I got is for nothing from our local Glazier who bevelled/ground all arrises, edges and corners. I have another smaller thinner one too.


The layout could be done on a bandsaw or tablesaw table with equivalent accuracy without having to clear off the mill table. Mine usually has a vise or dividing head in the middle of it. But if that is your only flat surface then you could eliminate the glass altogether and get just as good results for layout work.


Good - now you are "getting the message" - match the degree of flatness to the job requirements.


I fail to see from your pictures or words how the glass plate helps at all with layout work. In my opinion it looks like a completely superfluous waste of time and valuable machine table area.

Did I miss something.


Yes - the glass is wider than my mill table - increases my work area.

-DU-


For what its worth, I dropped that "fragile" (toughened) glass plate onto its corner from shoulder height, dropped it onto a brick (on its flat) from shoulder height and put a 2" bar under it (accross its width) stood on both ends and while it may have bent a little (from which it recovered to "flat" it nether fractured not did it have any permanent bend or whatever.

So I reckon I gave it a good run for its money and it came out OK.

This is "safety" glass as used in commercial windows, doors etc. so it had a good pegigree.

If I need any more - say for the grinder beds or magnetic chucks, its only a 5 minute drive in and same back and we pass it at least 3>4 times a week.

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

oldtiffie
04-17-2012, 02:26 AM
Originally Posted by oldtiffie

.RC.

See my previous reply to Forrest and others that my glass plate is used fully supported on my mill table specifically for setting up and marking out purposes and NOT (repeat) NOT as a surface plate.


Til you break it.


Forrest - see my previous post to Void.

Black_Moons
04-17-2012, 02:39 AM
Not sure what the sharpening stone is doing on there. Were you dressing down the burrs on your glass?:confused:
Personally, I would never put a sharpening stone on a "precision" surface with other precision surfaces on there all at the same time. Certainly on a cleared mill table or fixture to dress down burrs and high spots, then remove it and clean away any grit before anything else touches that surface.

That glass plate with all the stuff on it is just about as flat as your mill table. So would a 1/4" thick plate of glass or even a 1/8" thick one.

I fail to see from your pictures or words how the glass plate helps at all with layout work. In my opinion it looks like a completely superfluous waste of time and valuable machine table area.

Did I miss something.

-DU-

Nope. But as that pic is over 3 years old, I doubt he remembers what the sharpening stone was for either.

(First posted http://bbs.homeshopmachinist.net/archive/index.php/t-37769.html )

Glass, Like all materials bring as rigid as wet noodles when comparing support lengths of inches to deflections of thous, Will deflect 0.001" with just a few lbs placed on them when only 1/2" thick and on a non flat surface like a mill table.

I also wonder who among us actually believes there (Asian import) mill table is flat to within 0.0005" let alone better. I sure don't. If I had to guess, I would think 0.003~0.005" over the entire table.. Unloaded. More if you put anything on it where its not supported by the ways.

I am sure that tape its on is accurate to within 0.0001" too!

There are VERY good reasons that even the cheap, $60 import surface plates are 4" thick for just 24x16" size.

The Artful Bodger
04-17-2012, 02:47 AM
Hmmmm.... how about a glass plate supported by a few inches of concrete?

(Glass placed on wet concrete avoiding as much trapped air as possible then vibrated thoroughly.)

Black_Moons
04-17-2012, 02:53 AM
Hmmmm.... how about a glass plate supported by a few inches of concrete?

(Glass placed on wet concrete avoiding as much trapped air as possible then vibrated thoroughly.)

Concrete shrinks as it sets. I would assume that the shrinkage is not even and would warp the plate.

Better then just a plate I would suspect however, since it would at least help deflection if it was a few inchs thick.

The Artful Bodger
04-17-2012, 03:10 AM
Concrete shrinks as it sets. I would assume that the shrinkage is not even and would warp the plate.

Better then just a plate I would suspect however, since it would at least help deflection if it was a few inchs thick.


Just as well then I had no intention of actually doing that!:)

oldtiffie
04-17-2012, 03:19 AM
I suggest that some of those with quite subjective opinions on the strength of glass in general and toughened float glass in particular substantiate their claims and opinions to bring them the/an objective and qualitative level by testing a bit of that glass - first loaded at its ends and supported at its centre and record the result as a simply loaded beam.

Now support it as a beam with a uniformally distributed load with equal loads placed at equal centres at an equal number of equally spaced supports (say 100mm/4") - whch is the case with my float glass plate on my mill table.

I am going to be very interested in the results as well as sensible replies (not just opinions, wild ar$ed guesses and smart arses).


There are processes that increase the strength of glass. Toughening glass takes the glass to a temperature where it becomes flexible again and then it is chilled evenly and rapidly. The outer surface is chilled quicker than the inner glass. Because the core is trying to contract and the outer surfaces are already chilled the outer surface is being compressed while the core is under tension. The compression at the surface is pulling the glass together so any flaws are being closed rather than being free to open. It is only when the compressive strength is overcome that the glass will fail. The energy stored in the glass is released and the glass breaks in the characteristic form of toughened glass. Toughened glass is predictably 5 times stronger that annealed glass of the same thickness.

from:

http://www.pilkington.com/Europe/UK+and+Ireland/English/Building+Products/Pilkington4Architects/reference/Functions+of+Glass/MechanicalFunctionsofGlass/glass+strength.htm

mike4
04-17-2012, 03:38 AM
I think the biggest concern with glass is it is not stiff enough in the sections we normally see...

Put it on a curved surface and it will bend to that curvature...

I have seen one image of a glass surface plate, and it must have been 3 inches thick and only 12 inches across...
That is similar to the one which I saw at Uni when working with laser alignment gear.
I wasnt going to use glass plates for anything except maybe lapping in the shop as they probably would have a short life (too fragile )

The cast iron plate in the original post could be salvaged if you wanted to scrape it to flat , but looking at the photos I would either not buy it or would send it to be ground first to remove most of the deeper dings.

Michael

Void
04-17-2012, 04:01 AM
oldtiffie,

The Young's modulus for glass(es) varies between 50 and 70 GPa. There may be some glasses that have a higher modulus of elasticity but I couldn't find any.

Iron and steel has a Young's modulus that varies between 190 and 210.

Young's modulus "stiffness" is different from "toughness." In engineering the terms are not interchangeable. "Strength" is a vague term, engineering wise, unless it comes with another term such as "tensile strength" or "compressive strength" or "shear strength."

What I am saying is: "toughening" glass doesn't necessarily make it "stiffer."

I don't have any 1/2" "toughened float glass" handy... but you do. Right in that picture. Put a couple of those 123 blocks under it near the ends. Not 4" apart*. Put one of your DTIs with the base on the mill table. Start loading it up with stuff you have at hand (surface gages, 123 blocks, etc...) How much weight to deflect it a thou in the middle? Sweep the whole length with the gage.

If you have a half inch thick rectangular bar, steel or iron, set it up between the blocks and repeat the experiment. How much does the steel deflect using the same weight?

*The reason I say not 4" apart is because the piece is MUCH longer than 4". If you have about a 6" long piece that would be fine for testing it between a could of 123 blocks 4" apart.
For minimal deflection of an evenly loaded beam you would want to use the Airy points as support points along the length.

You have all the stuff right there. You do it.
While I can't speak for others I will say that I will take you at your word on the results (unless they are very far off from the theory.)

-DU-

mike4
04-17-2012, 04:19 AM
I have been following this with some interest , I have one more question , and dont take it the wrong way .

I would like to know if anyone here routinely works to a tolerance of 0.0001"or 0.0005"
As a lot of the equipment in most shops would be way less than that .

Often it is only necessary to go to 0.0015 or even heaven forbid 0.005.

As I work in the real world of customers who want equipment to work after it is repaired ,not fail after a couple of days or hours of work I have found that in some situations very close tolerances can and have been the cause of a very expensive failure.
I am not knocking the need for precision or accuracy ,but like many things it has its place, and in certain very stressful applications a little free play can save a shaft or bush from binding due to bending or frame twist .
Michael

Void
04-17-2012, 04:29 AM
Good question.

In my case: When the job calls for +/- 0.0002" on features I work to tenths on those features, routinely.
When it calls for +/- 0.001" on features I work to half a thou on those features, routinely.
And so on.

Some parts have features that are within a teenth, and some features are a thou or two, and some are a tenth or two.

It all depends on what is called for. Since I do prototype work on scientific instruments it is routine to have parts with all those kinds of tolerances.

-DU-

mike4
04-17-2012, 04:34 AM
Good question.

In my case: When the job calls for +/- 0.0002" on features I work to tenths on those features, routinely.
When it calls for +/- 0.001" on features I work to half a thou on those features, routinely.
And so on.

Some parts have features that are within a teenth, and some features are a thou or two, and some are a tenth or two.

It all depends on what is called for. Since I do prototype work on scientific instruments it is routine to have parts with all those kinds of tolerances.

-DU-
Thanks for the quick reply ,thats one area that I had forgotten.
I work in many areas but most dont require that degree of tolerance .
Michael

.RC.
04-17-2012, 04:40 AM
I have found that in some situations very close tolerances can and have been the cause of a very expensive failure.


You might be confusing nominal size to tolerance there...

Something is designed to be such a size, then a tolerance is applied to it how much bigger and smaller it can be and the device still work...

But as to who here would routinely work in 2 microns sizes...

I don't as you would need a tight grasp on many variables to be able to work to such a tolerance.. Variables that you do not to consider on run of the mill stuff..


However when discussing scraping and machine tool reconditioning those sorts of tolerances come into play, as you want your machine to end up as good as you can get it so it has a long life before it is worn out....

Also this is the Home Shop Machinist forum, I think there is a little bit of pride here for participants to be building say a model engine with all sizes to as close to nominal as they can get them.. After all there is no foreman breathing over your shoulder to get the job done as quick as possible...

Black_Moons
04-17-2012, 04:40 AM
I have been following this with some interest , I have one more question , and dont take it the wrong way .

I would like to know if anyone here routinely works to a tolerance of 0.0001"or 0.0005"
As a lot of the equipment in most shops would be way less than that .

Often it is only necessary to go to 0.0015 or even heaven forbid 0.005.

As I work in the real world of customers who want equipment to work after it is repaired ,not fail after a couple of days or hours of work I have found that in some situations very close tolerances can and have been the cause of a very expensive failure.
I am not knocking the need for precision or accuracy ,but like many things it has its place, and in certain very stressful applications a little free play can save a shaft or bush from binding due to bending or frame twist .
Michael

I believe you are confusing tolerance for clearance. tolerance is how accurate the parts must be made. IE this hole must be 1" to 1.002"
Clearance is the relation to two parts. This 1" to 1.002" hole has a 0.990" to 0.992" pin in it. The tolerance is +- 0.001. The clearance is 0.008 to 0.012, The clearance has a tolerance of +-0.002

Low clearance parts need a small tolerance to maintain a small tolerance for the clearance.
Large clearance parts can be low or high tolerance.

Joel
04-17-2012, 04:44 AM
Corning's Gorilla Glass is some interesting stuff.
It is exceptionally flexible:
http://www.youtube.com/watch?v=D4j4wqA2Mko

The Young's modulus is 73.3
More specs:
http://www.corning.com/docs/specialtymaterials/pisheets/PI2317.pdf

http://www.corninggorillaglass.com/innovating-with-gorilla

Forrest Addy
04-17-2012, 04:49 AM
Guys, Old Tiffie is gaming us. He LOVES this Yabbut game. He plays it expertly. The premise is he's unjustly taken to task and the pay off is he gets to chide us for being obtuse and missing his (alleged) points.

Don't get me wrong. Tiffies is a smart dude and his supporting material is quite often spot on. I've learned more than a few lessons from him and take his credible points seriously. But after his point is made and the discourse it engenders dies down, he refreshes the controversy with yet another position, missing point, allegation of misunderstanding etc leading to endless point/counterpoint responses.

OK I'll briefly play the game. Now he's defending glass in a machine shop as a working surface. In all the shops I've been in where the subject came up glass on the production floor is verboten as a safety hazard and as too fragiie except for plan offce or tool room windows, frangible parts of the fire alarm system etc. Avoidance of glass in the production shops extends to the safety glass and temperd glass originally furnished as chip enclosure windows of older machines. The first replacement is usually Lexan in most shops I've been in.

Tiffie use whatever floats your boat in your own shop.

Yes, you are right: well supported glass will make a quite accurate flat working surface but it's disadvantages, uncertifiability, fragility, and its readiness to scratch, not to mention its graceless failure mode of utter fragmentation makes it a liability on the shop floor.

Thus, Tiffie, you do a disservice to the less experienced among us by advancing penny-wise pound-hazardous folly of glass as a working surface. If supported glass can be accurate enough for non critical work but it's still glass, frangible, fragile, scratchable, bust in a million pieces glass "toughened" or not. Drop a V block on its corner and glass - any glass - shatters. The failure is the same - cracks, cubes, or shards - only the threshold energy of rupture is different.

The rest of you: I hear you. When you have to work to 0.0001" or microns you have to have tracible references -including flats - to support it. The usual rule is your apparatus has to be 10x as accurate as the tolerance your're working to. You can get by with 4x but you have to be careful and your interpretation of cert sheets and error maps have to be not only inspired but acceptable to third party inspection.

The rub comes when you have to make stuff and it has to fit the stuff made in Sioux City, Tashkent, Helsinki, or Terra del Fuego. If your stuff aint right no amount of alibi will make it right. The only thing that will close the doors of a shop quicker than tax trouble is inaccurate work. Period. Inaccurate is inaccurate whether it's measured in 0.0001" or sixteenths. Tolerance isn't all: ask the fab shop that made two east spans for a counterbalanced bascule bridge.

mike4
04-17-2012, 05:16 AM
I believe you are confusing tolerance for clearance. tolerance is how accurate the parts must be made. IE this hole must be 1" to 1.002"
Clearance is the relation to two parts. This 1" to 1.002" hole has a 0.990" to 0.992" pin in it. The tolerance is +- 0.001. The clearance is 0.008 to 0.012, The clearance has a tolerance of +-0.002

Low clearance parts need a small tolerance to maintain a small tolerance for the clearance.
Large clearance parts can be low or high tolerance.
I do know the difference ,thanks, in the two most expensive failures the parts were measured during assembly by the manufacturers techniians , they were all spot on to the 0.0025 which is mid range for the part in question , the bushing that it was fitted into was slightly oversize but within specs of +/_ 0.002 also .
However we discovered that the machines frame was twisting about 0.25" which caused a binding and destruction of the bushes on both sides after 4 hours of operation.
The mods were to increase the "slop" allowed then it could operate for months on a 24/7 basis without a problem.
If the machine was operated on a flat surface all would work , but the designer didnt think that anyone would use it on an uneven surface as is often the case in a quarry.
The other was more costly for me as I had followed the manufacturers refurbishment procedures and used OEM parts .
All was well until the operator drove it up a ramp with a 4 inch block of wood under one side the result was a split in the cast steel frame which cost me thousands.
Ouch!
Thats why I am asking the sorts of questions that I am , yes I am not a true HSMer as I use my gear to earn money , however I do take pride in my work and also like to get up the noses of those who never have to take responsibility for other peoples equipment on a daily basis .
Often there is no allowance made for failure ,there is only one acceptable outcome it operates as expected ,with no funny noises .

oldtiffie
04-17-2012, 06:30 AM
https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcQ4_n5k6YXbVI6TbcTx0Zwng8NHViQ1a F-BORgyfytcE5V8RQEm

oldtiffie
04-17-2012, 06:45 AM
https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcQ4_n5k6YXbVI6TbcTx0Zwng8NHViQ1a F-BORgyfytcE5V8RQEm

J Tiers
04-17-2012, 08:21 AM
Not all jobs are QA-ed or QC-ed and if the operator is within his limits as per the client drawings or brief he has met his obligations to the client. It is up to the client to specify limit and tolerances etc. - even if he is knowledgeable enough to agree with those suggested by the operator.

All of this level of stuff requires a rigid adherence to proceedures and "paper-trail" aka "traceablity".

It almost always required that the operator and his shop be QA/QC certified.

I doubt that too many here are certified or work to those QA/QC plans and proceedures.

So lets get back to day-to-day average HSM shops - and surface plates. ...............................

Fine..... GAME OVER.

Let's limit this to the "home shop"...... Presumably that means a drill press, files, a worn-out Atlas lathe, and a Western Auto grinder with the gray stones on it, presided over by "Bubba", for whom it is "plenty good enough for me".
Tolerances of 0.02" or more, and a "this just gotta fit that" standards scheme. Shop used for making incidental bushings and spacers for other projects.... much like the drag racers I bought a lathe from last year..

If that's what you mean by a "home shop", then most of what even you, Tiffie, have said is null and void, and your standard set of pictures and drawings are showing measuring equipment that is "too highfalutin' and preeee-syse", "just fer them city slickers as thinks they is so dang much smarter than us".

Then there is an "other" sort of home shop.... producing these:

http://www.youtube.com/watch?v=VWn8gQ9Ykpk&feature=player_embedded

http://www.minimodelengines.com/Feature4C.htm

While I agree that these can be produced with a "this gotta fit that" approach, once the "that" is made, the entire SIZE of the "this" may be comparable to just the tolerances in "Bubba's" shop.

Most folks will NOT be making things that have to fit with another part made in Dubrovnik, but that does not negate the need to be precise in even making "this fit that".

And, of course, when reconditioning machinery, precision of at least flatness rapidly gets into the tenths.

Yep, you are "gaming us"...... it's cheap, easy, and you have the materials and illustrations at hand.... we don't know if you have already "binned" all that stuff, but it doesn't matter, you still have the pics.

Oh, and if you are "supporting" your thin glass on another surface....... THE FLATNESS OF THE THIN GLASS IS GOING TO DEPEND ON THE FLATNESS OF THE OTHER SURFACE.

And, if you use rubber foam tape, as it seems, then the glass will be ripply like the lake in a breeze.

Yep, Bubba, you DO be gamin' us.

Mcgyver
04-17-2012, 09:49 AM
I would like to know if anyone here routinely works to a tolerance of 0.0001"or 0.0005"
As a lot of the equipment in most shops would be way less than that .

Often it is only necessary to go to 0.0015 or even heaven forbid 0.005.



Mike I think it is a very good point & question. I think the first part of the answer is you want your most accurate tools to meet the most exacting requirements you'll ever have, not the run of mill. Buying a 10ths mic doesn't mean everything you do is tenths, but its what you need when you're machining a shaft for a roller bearing interference fit.

Secondly, there is a home shop twist that increases the accuracy required of references such as surface plates: scraping. Its less common in comerical settings perhaps, however quite prevelant in home shops as we satisfy champagne tastes on ginger ale budgets. Many of us buy older best of class machines for small dollars and recondition them. Scraping and making its required references is work to .0001 and there are lots of home shop guys doing it.

Rosco-P
04-17-2012, 08:16 PM
that reminds me of that to horrible creature too many tools or something like that? now there was wanker!

the least these guys could do is bring some humour with it and character damn it!....I mean who didn't tune in when Airsmith was firing on all brain cells, and Millman, now there was a guy you could really take some grumpy lesson from. classic stuff. This new breed of trolls, i dunno, its like bad pop music, lots of noise but its missing the hook

:D
:D
:D

Airsmith lives on: advice; reviews; lessons; and such: http://www.youtube.com/user/KevinMillard68/videos

mike4
04-17-2012, 08:51 PM
Fine..... GAME OVER.

Let's limit this to the "home shop"...... Presumably that means a drill press, files, a worn-out Atlas lathe, and a Western Auto grinder with the gray stones on it, presided over by "Bubba", for whom it is "plenty good enough for me".
Tolerances of 0.02" or more, and a "this just gotta fit that" standards scheme. Shop used for making incidental bushings and spacers for other projects.... much like the drag racers I bought a lathe from last year..

If that's what you mean by a "home shop", then most of what even you, Tiffie, have said is null and void, and your standard set of pictures and drawings are showing measuring equipment that is "too highfalutin' and preeee-syse", "just fer them city slickers as thinks they is so dang much smarter than us".

Then there is an "other" sort of home shop.... producing these:

http://www.youtube.com/watch?v=VWn8gQ9Ykpk&feature=player_embedded

http://www.minimodelengines.com/Feature4C.htm

While I agree that these can be produced with a "this gotta fit that" approach, once the "that" is made, the entire SIZE of the "this" may be comparable to just the tolerances in "Bubba's" shop.

Most folks will NOT be making things that have to fit with another part made in Dubrovnik, but that does not negate the need to be precise in even making "this fit that".

And, of course, when reconditioning machinery, precision of at least flatness rapidly gets into the tenths.

Yep, you are "gaming us"...... it's cheap, easy, and you have the materials and illustrations at hand.... we don't know if you have already "binned" all that stuff, but it doesn't matter, you still have the pics.

Oh, and if you are "supporting" your thin glass on another surface....... THE FLATNESS OF THE THIN GLASS IS GOING TO DEPEND ON THE FLATNESS OF THE OTHER SURFACE.

And, if you use rubber foam tape, as it seems, then the glass will be ripply like the lake in a breeze.

Yep, Bubba, you DO be gamin' us.

If the reference to "Bubba's " shop is in anyway a derogatory remark aimed at my work and the machinery which I work on , then I will say its GAME ON .
I can and am often required to work to many different tolerances , normally on new machines , however there are times when due to wear and deformation in other areas the only way to stay within a reasonable time frame and budget then the parts have to be made to fit sometimes under size or slightly over size what ever the case may be ./

Contrary to popular beleif that can take some skill as you only get one chance , we are not talking about 1/4" diameter parts which are 1/2" long .

The sub assemblies are 45mm thick and in the range of 1.2 m wide and often 3-4 m long , not the sort of thing that you cart around and fart about with.

The parts that we fabricate and then machine are in the 12" dia and 6-8 inches long machined to take commercially available bearings and seals , the only divergence from original is that it has to be made fit into the existing holes in the frames which are machined in the field with portable equipment .

So unless you actually do similar work in the field , dont criticise what you dont know .

Michael

J Tiers
04-17-2012, 10:31 PM
If the reference to "Bubba's " shop is in anyway a derogatory remark aimed at my work and the machinery which I work on , then I will say its GAME ON .


In case there is any question......

I was not even thinking of you, and I have forgotten, if I ever knew, what you work on.......

And, it isn't even really "derogatory" to "Bubba".... He's happy with what he does, and I have no problem with that......

The problem comes out when

1) some folks, who do that sort of work (Since I don't know what you do, that is NOT you), want to tell everyone else that they can't be working any closer either "it's good enough for me, who do you think YOU are to work closer than that?"...... (I don't recall you doing THAT either). They will say "you don't need that fancy granite flat, a piece of glass or slab of counter works fine for me and it's good enough for you too."

OR

2) Other folks, who spent their working careers working to tenths or better in the toolroom, start claiming that "this" or "that" *cannot be done in the home shop*. When they think "home shop" they think of Bubba's shop, with the Western auto drill press and worn out Atlas, plus the grinder with its well-glazed gray stones..... Those snooty folks will say "you don't know what to DO with a good surface plate, just use some glass or a slab of counter".

There are some home shops whose owners have the equipment and skill to do more varied close tolerance work than many a commercial shop. So much for "home shop".

Ain't either of those attitudes worth a handful of 1018 swarf.

People do all sorts of different things in their shops, and I have no problem with that. Even the drag racers that I got the Rivett from were doing OK.... small needs, little machining skill, but it got them what they needed. It was the swarf and grit and grime all over the lathe that earned them my disrespect.

mike4
04-18-2012, 03:42 AM
In case there is any question......

I was not even thinking of you, and I have forgotten, if I ever knew, what you work on.......

And, it isn't even really "derogatory" to "Bubba".... He's happy with what he does, and I have no problem with that......

The problem comes out when

1) some folks, who do that sort of work (Since I don't know what you do, that is NOT you), want to tell everyone else that they can't be working any closer either "it's good enough for me, who do you think YOU are to work closer than that?"...... (I don't recall you doing THAT either). They will say "you don't need that fancy granite flat, a piece of glass or slab of counter works fine for me and it's good enough for you too."

OR

2) Other folks, who spent their working careers working to tenths or better in the toolroom, start claiming that "this" or "that" *cannot be done in the home shop*. When they think "home shop" they think of Bubba's shop, with the Western auto drill press and worn out Atlas, plus the grinder with its well-glazed gray stones..... Those snooty folks will say "you don't know what to DO with a good surface plate, just use some glass or a slab of counter".

There are some home shops whose owners have the equipment and skill to do more varied close tolerance work than many a commercial shop. So much for "home shop".

Ain't either of those attitudes worth a handful of 1018 swarf.

People do all sorts of different things in their shops, and I have no problem with that. Even the drag racers that I got the Rivett from were doing OK.... small needs, little machining skill, but it got them what they needed. It was the swarf and grit and grime all over the lathe that earned them my disrespect.

Ok that clarifies the statement a lot .

I to have equipment which is locked away and only used for high spec jobs with traceable specs on equipment ,costs a bit but the work pays well.

There are also the run of the mill mics, plates etc which are in daily general use , still treated with respect , but not as high a quality .

We may be in different locations but our equipment is respected to similar standards.

Although mine may not always be as clean as others due to time spent on work , they are kept to what I call trade clean , no piles of crap or gunk on everything.

Michael

Greg Q
04-18-2012, 04:31 AM
Mike, to add one more voice to the sidebar issue of who works to what tolerances: I purchased formerly high end European machine tools because I am not a fan of H & F. In fact, I wouldn't micturate upon them if they were aflame.

So, I had to aquire the tools and knowledge in order to restore my machines. Scraping being the most radical, yet esoteric and expensive among them. Thus, I work to 0.0001" , but only when fifty millionths is too ellusive. Since I lack a precisely climate controlled shop I have to pick my times when chasing crazy small values when making gauges with which to work on my machines. It has been a s-l-o-w process, but I don't expect the result to be as much fun as the journey.

When my machines are finally as good as I can make them I will revert to being a regular HSM hack...0.1 tolerance on some days, 0.005 on most days, but secure in the knowledge that I can hold my tongue just right and get a part within a tenth or two because my machine tools will not be a hurdle in that pursuit.

Its an odd hobby...amateur precision; perhaps on the same plane as hobby woodworkers sharpening chisels with 1 micron diamond paste, but the results of making a part with uncommon precision are often their own reward.

(having said that, I understand that I wouldn't last until morning tea in a commercial setting; but then again, I don't have to. Hence the "H" in "HSM.)

Greg
Melbourne

mike4
04-18-2012, 06:42 AM
Mike, to add one more voice to the sidebar issue of who works to what tolerances: I purchased formerly high end European machine tools because I am not a fan of H & F. In fact, I wouldn't micturate upon them if they were aflame.

So, I had to aquire the tools and knowledge in order to restore my machines. Scraping being the most radical, yet esoteric and expensive among them. Thus, I work to 0.0001" , but only when fifty millionths is too ellusive. Since I lack a precisely climate controlled shop I have to pick my times when chasing crazy small values when making gauges with which to work on my machines. It has been a s-l-o-w process, but I don't expect the result to be as much fun as the journey.

When my machines are finally as good as I can make them I will revert to being a regular HSM hack...0.1 tolerance on some days, 0.005 on most days, but secure in the knowledge that I can hold my tongue just right and get a part within a tenth or two because my machine tools will not be a hurdle in that pursuit.

Its an odd hobby...amateur precision; perhaps on the same plane as hobby woodworkers sharpening chisels with 1 micron diamond paste, but the results of making a part with uncommon precision are often their own reward.

(having said that, I understand that I wouldn't last until morning tea in a commercial setting; but then again, I don't have to. Hence the "H" in "HSM.)

Greg
Melbourne
Greg ,
You obviously like to work with good equipment , as do most of us ,.

In some regional areas it is not always possible to buy or "find" machine tools in any condition , therefore if you need to fit out a shop it is necessary to buy from machinery dealers , we dont have many to choose from unfortuneately and often the Chinese machines are adequate to do not so high tolerance jobs like making a bearing cover or threading a bolt on Sunday when the suppliers are closed.

I have mre high end machines for heavy accurate work , purchased second hand from businesses which were closing due to retirement of owners.
As I currently use themachines as part of my work I dont have time to spend on restoration.
One day maybe(dreaming)
Michael

Greg Q
04-18-2012, 10:02 AM
Mike...just to be clear, I have no gripe with Chinese machines because of their country of origin, rather with the importers who specify minimum acceptable quality for maximum obtainable profit.

I have seen a Deckel copy made by the Bejing Instrument Something or Other Company that was delightful, and I would have been happy to own it. But branded oriental machines are the rare exception to the typical crud that we see from the bargain importers. Ditto Chinese commodity priced motors, bearings, cars etc. No thanks. I try not to be a snob, but by the same token I will be damned if I am going to pay 4,000 bucks for a lathe kit which requires as much tuning up as a superior $2,000 used deluxe machine.

Horses, courses, etc

lazlo
04-18-2012, 10:17 AM
This thread is a classic -- almost up there with the Mall Ninja.

It made me laugh, it made me cry, ... :D

Airsmith: RIP -- there's a new jester in town ;)

J Tiers
04-18-2012, 08:34 PM
Airsmith: RIP -- there's a new jester in town ;)

There's a second...... go check out the pump thread....... for some truly "hermetic" reasoning.....

lane
04-18-2012, 10:09 PM
Ok I will jump in . Read the first two pages then quit for a few days . It got so big I decided i had better read it all.
My only question is. What in the world is a Home Shop Machinist going to build that needs this kind of accuracy. People arguing over how flat something is are is not ,and what it takes to get their. Your mill table is a flat as you will ever need any thing you make to be. I use the table on my big Grob band saw to lay parts out on . Because it is more than flat enough. you are not working to light bands . And my surface grinder will get things as flat as I can measure with what I have that I can trust. Yes their is super high precision for flat, parallelism, and size but how many of us are most shops even need it .I have worked in many shops that did not even know what a surface plate was , and some where we measured in light bands. It just depends on what you are doing and I don`t think any of us are doing that kind of work . some may just want to know about it . I know enough to know better. Some one was talking about the precision of Moore jig borers and such. To day modern cnc will out do them and Jig Bores are cheap on E-Bay.

mike4
04-19-2012, 12:56 AM
This thread is a classic -- almost up there with the Mall Ninja.

It made me laugh, it made me cry, ... :D

Airsmith: RIP -- there's a new jester in town ;)

Clowns abound on this site.
Michael

.RC.
04-19-2012, 05:28 AM
Sorry but I don't agree with this statement.
It seems we have two schools of thought, the old timers who say it has to be planed then hand scraped to flat and the more modern school that says ground, then possibly followed on by hand scraping.

Planing is going to be flat but have troughs on from the planing tool. Grinding is going to be flat with tool marks from the grinding process but no troughs.

Grinding can easily get to 4 Um and as close as 2Um, planing can get nowhere near this.

If scraping is the ultimate surface then why are linear rails not scraped or bearing tracks?

Why do they have to resort to grinding ?

Look at any modern mass produced machine tools, capable of working to far greater tolerances than any previous machines before and not one scraped surface in sight.

I think it is complicated, more complicated then it looks initially...

From what I understand with flat ground ways running on flat ground ways you need ample and reliable pumped pressure lubrication as dead flat on dead flat with intermittent lubrication leads to the oil squeezing out and leads to galling...

Scraping by imparting divots into the surface creates two things... Firstly it creates tiny oil reservoir's on the surface morso if frosted... This means intermittent lubrication can happen and you still get enough lubriction to stop galling at slow speeds..... Modern CNC speeds probably throw that out the window.... After all it is very common to see shaper and slotter rams with galling and they can run at fastish surface speeds..

Secondly the divots reduce the surface contact area.... But this increases as wear occurs, until you get 100% coverage, the oil squeezes out and you get galling... But by this time the ways are probably banana shaped anyway..

Thirdly the less contact area of a scraped surface means less slip stick, i guess this is important on CNC machines and big big machines...

Once slideway grinding started becoming common place I guess we also started to see an explosion in hardened ways..... Hardened ways cannot be economically scraped, and in any case slideway grinding was found to be accurate enough.. but, the mating soft part that runs on the hardened long ways was and still is scraped, you just cannot see it until you pull it apart... Also it is scraped to repair alignments, To fix that V way where the small sliding part has an incorrect angle that is out by only a fraction of a degree.. Probably less of a problem these days with CNC angular heads on grinders though...

There is probably more to it, like the way jog borers and grinders were scraped over ground, but I think I have said enough...

This is just info I have picked up in bits and pieces and put it together how I think it works... Could be wrong..It is a complicated subject...

oldtiffie
04-19-2012, 07:49 AM
Ok I will jump in . Read the first two pages then quit for a few days . It got so big I decided i had better read it all.
My only question is. What in the world is a Home Shop Machinist going to build that needs this kind of accuracy. People arguing over how flat something is are is not ,and what it takes to get their. Your mill table is a flat as you will ever need any thing you make to be. I use the table on my big Grob band saw to lay parts out on . Because it is more than flat enough. you are not working to light bands . And my surface grinder will get things as flat as I can measure with what I have that I can trust. Yes their is super high precision for flat, parallelism, and size but how many of us are most shops even need it .I have worked in many shops that did not even know what a surface plate was , and some where we measured in light bands. It just depends on what you are doing and I don`t think any of us are doing that kind of work . some may just want to know about it . I know enough to know better. Some one was talking about the precision of Moore jig borers and such. To day modern cnc will out do them and Jig Bores are cheap on E-Bay.


+1 Lane.

I've been banging that drum since forever. I only need just a bit more "flat" than the job requires.

Some (many?) just want more just for the sake of having it (and bragging rights?).

There is all too often a considerable gap between what people need and what they want.

The "need" is - or should be - based on job functionality.

My slip gauges and surface plates rarely see the light of day and if they do I seriously ask myself "Why? What have I done wrong that got me here?"

My mill (and "float glass plate") and my grinder tables and the top of my magnetic chucks get a good work-out though as does my 0.01mm (~ 0.0004" - 4 tenths) dial indicators and metric micrometers.

Most turning and milling job limits are at or over +/- 0.025mm (~ 0.001" - a "thou") and many are well over it.

If I have those sorts of tolerances or limits I use them to the full.

J Tiers
04-19-2012, 08:21 AM
The problem comes out when

1) some folks, who do that sort of work , want to tell everyone else that they can't be working any closer either "it's good enough for me, who do you think YOU are to work closer than that?"...... . They will say "you don't need that fancy granite flat, a piece of glass or slab of counter works fine for me and it's good enough for you too."

OR

2) Other folks, who spent their working careers working to tenths or better in the toolroom, start claiming that "this" or "that" *cannot be done in the home shop*. When they think "home shop" they think of Bubba's shop, with the Western auto drill press and worn out Atlas, plus the grinder with its well-glazed gray stones..... Those snooty folks will say "you don't know what to DO with a good surface plate, just use some glass or a slab of counter".

There are some home shops whose owners have the equipment and skill to do more varied close tolerance work than many a commercial shop. So much for "home shop".

'nuff said..........................

Mcgyver
04-19-2012, 09:00 AM
well you got the OT vote of confidence so mayby I should just change my mind :D


Ok I will jump in . Read the first two pages then quit for a few days . It got so big I decided I had better read it all.
My only question is. What in the world is a Home Shop Machinist going to build that needs this kind of accuracy. People arguing over how flat something is are is not ,and what it takes to get their. Your mill table is a flat as you will ever need any thing you make to be. I use the table on my big Grob band saw to lay parts out on . Because it is more than flat enough. you are not working to light bands . And my surface grinder will get things as flat as I can measure with what I have that I can trust. Yes their is super high precision for flat, parallelism, and size but how many of us are most shops even need it .I have worked in many shops that did not even know what a surface plate was , and some where we measured in light bands. It just depends on what you are doing and I don`t think any of us are doing that kind of work . some may just want to know about it . I know enough to know better. Some one was talking about the precision of Moore jig borers and such. To day modern cnc will out do them and Jig Bores are cheap on E-Bay.

This is a frequent theme for you "bhaaa, good enough for the homeshop". Maybe yours, but whether you're correct or not for the next guy is a function of what he is doing in his shop. that's no slight to you, your work has always looked good, and for what you build and do you have your set of requirements...but it doesn't change the fact that is the case for your shop, not necessarily the next one.

what would you need it for in a home shop? what would you need it for a non-home shop? Same answer basically. That a shop within x feet of a house vs. an industrial unit hardly dictates what goes on there :confused:

1) One shop I spend a lot of time in lately does super precision aerospace stuff: has state of the art CNC, hardinge lathes, matsura mills, wire edm, cmm etc. The regularly do more accurate work than I, and because of their equipment they don't use a plate, they don't need it. I don't have $500M mills, CMM and giant wire EDM's to control accuracy so don't rely on references like a plate. There's an example of a commercial shop doing more accurate work than me, limited use of plate.

2) Another shop I've been at a lot is a giant, does maintenance work for the oil sands. overlay welding and boring on the sides of D10 bulldozers etc. Guess what? they don't use many surface plates. Big stuff to bigger tolerances than I work on. There's an example of a commercial shop doing less accurate work than me, limited use of plate.

Point being that lots commercial shops don't use plates is meaningless insofar what someone else needs.

3) Then there is scraping, references and directly to the plate. If for no other reason that alone demands a quality plate. I don't think it would be stretch to say a high percentage of home shops scrape than commerical and since scraping is the 'closer' in this debate, what we really should be asking is 'what do all those commerical shops need a plate for" :D

4) One doesn't buy a tool for one or two standard deviations, you buy it to handle the extremes as well. The example I gave is a tenths mic. I or anyone else hardly measures in tenths for everything, but there are times when you strive to like roller element bearing fits. So you think it wrong to have a tenths mic because it only gets used 0.1% of the time?

Same with a surface plates. You want a surface to layout on. In today's age of CNC, commercial shops don't do much layout. We do. what are you going to do - your layout work on the mill? yeah right. So you need a surface to layout....doesn't it make sense to have it accurate enough to also do those more extreme things like making a scraping reference, checking for square and parallel etc?

I don't get this need to keep saying what you think you need should apply everywhere else. As you've noted, shops you've worked in have widely varying accuracy demands.....you think that variety stops because the shop is x feet from a house? Where I agree with you is that there are many have acquired things that they don't really need or that their work wouldn't demand, but 1) so what they're doing it for fun, and 2) its irrational to say everyone who has acquired said items isn't doing work that demands it

lazlo
04-19-2012, 10:59 AM
My only question is. What in the world is a Home Shop Machinist going to build that needs this kind of accuracy.

Lane, I think you're missing the point. The OP found a beat-up surface plate on Craigslist, and was asking if he should buy it, or go with an imported Chinese surface plate:



This popped up used - its supposed to be an old 18x18 calibrated surface plate with legs, but look at the big dings! They are asking $75, but after I saw the dings in the picture I am thinking a 12x12 granite one from shars for about the same price shipped is looking pretty good!

The point, IMHO, is not whether the OP, or any home-shop machinist, needs any arbitrary level of precision, it's whether there's any point in buying a beater surface plate.
Personally, I would go for the Shars plate.

Forrest Addy
04-19-2012, 01:06 PM
There will always be people who cannot imagine needs unlike their own. I've worked to many degrees of precision from excavation to high precision metrology.

I've found digging a string of post holes and holding the fence face an inch back from the surveyed line as challenging as anything I ever did in the machine shop.

The demands of every human activity requires care and attention if the results are to perform as required. Part of this care and attention is reflected by the degree of precision. If you as a home shop machinist feel .002" plenty close enough for any application should take comfort that no-one cares if you are outraged; you're speaking out of willful ignoorance. If you use that 0.002" for wood carpentry you're wasting time in needless precision. If you are fitting automotive pistons to their pins your work will be unbelievably crude.

Surface plates have to be flat and how flat depends on the degree of precision required. There are too many factors to list where early attention to precision pays off in final acceptability. With precision comes an inevitable residue of error. These errors if allowed to accumulate may in the end frustrate the final fits and alignments of the finished article.

I worked in industry my whole career. I'm used to calibration systems. I'm aware of the need for calibration standards in the shop and I'm failry well equipped to calibrate my own precision tools. I know the accuracy of al my tools and equipment where the knowledge is important. I maintain a rough paper calibration trail for most of my measuring tools.

I don't care abut 0.0001" for their own sake but I do care about results. If 0.0001" is the difference between success and failure then you can bet I will sweat that 0.0001."

A man scraping in a machine tool has to sweat the 0.0001" because the durabiility of the bearing surfaces he generates depends on it. The lubricating mode is boundry meaning the oil film is very thin. As it happens 0.0001" is not at all difficult to hit for a man with a scraper provided the reference he uses to develop that surface is flat. Hence a wise scraper hand is concerned for the flatness of the reference surface (his surface plate) he uses to validate intermediate references - straight edges, fitter's flats, scraped polygons etc - so he seeks "A" grade granite flats avoiding the "B" grade thinking the 2x greater precision - well he might be right.

OK THAT out to the way, re-scraping a worn surface plate requires another accurate plate or three close to the same size so they may be scraped together in sequenct via the "averaging or errors" method. It's generally simpler to buy a cheap granite plate and just use it it than to buy/borrow a granite plate and use it to re-scrape the iron one. The question to be asked is do you wish to have a freshly scraped cast iron plate in a place of honor and use it or spending $100 in cost and shipping for an import POS that's not only as accurate but maybe 5X as durable in everyday shop use? See my first post on this thread. I think my reasoning and supporting discussion still holds water.

.

oldtiffie
04-19-2012, 07:05 PM
Lane, I think you're missing the point. The OP found a beat-up surface plate on Craigslist, and was asking if he should buy it, or go with an imported Chinese surface plate:




The point, IMHO, is not whether the OP, or any home-shop machinist, needs any arbitrary level of precision, it's whether there's any point in buying a beater surface plate.
Personally, I would go for the Shars plate.

+1

Shars listing of surface plates:

http://www.shars.com/product_categories/search/?search=surface+plate

lane
04-19-2012, 09:02 PM
No I knew what the OP was talking about . The old beater plate he showed would make a nice welding bench and a cheap import plate would be the best deal I agree. i have a 12x 18 inspection grade plate my self ,Bought 30 + years ago but again it gets used about a few minutes every 5 are so years ,If checking something of the grinder .
And again I know their are those out their who want to scrape something . been their and done that enough to know never again . Have a good Bax Scraper just taking up space along with a straight edge I gave $1000.00 for new.
Call a home shop what you want ,But to me it is to play in ,its for a hobby not to be making money with. I turn down jobs monthly from people wanting things fixed are built. I make my living doing this stuff every day for some one else . When I come home I want to build what I want and do it my way .
Spent 20 years building specialized equipment to automate a process made the parts inspected the parts some times designed the parts and assembled and aligned the machines even helped wire them . So I know what precision is all about .
Besides not knocking any one Heck I am just as hard headed as you are. But I know enough to know you are NOT going to change some one`s mine once he is set in his ways. Even though some of you try mighty hard to do that I am not trying to change your mine because I know i cant . I was just voicing my opinion. So good night to all I will go read PM now.

Mcgyver
04-19-2012, 10:13 PM
Call a home shop what you want ,But to me it is to play in ,its for a hobby not to be making money with. .

...ok....and that affects the accuracy one wants to/needs to accomplish how? :confused:


Besides not knocking any one

No?


It just depends on what you are doing and I don`t think any of us are doing that kind of work . some may just want to know about it . I know enough to know better.

sounds like a knock to me, or at least a hard tap. It comes across as, perhaps unintended, hubris: based on the fact that I don't need it, no one else does....the only way this can be true is if everyone else was doing work lesser or maybe equal work. Maybe you didn't intend that, but it's what you do when you start stating what everyone elses needs are.


Heck I am just as hard headed as you are. But I know enough to know you are NOT going to change some one`s mine once he is set in his ways.

Minds are no more the same any more than workshop activities are. I'm sure my self assessment is rosier than any third parties :) but I try to distinguishing between what I know from opinions, beliefs, conjecture etc and to avoid the character flaw of needing to be right. So all and all, I ought to be an easy mind to change :D.... but its battle scared and savvy - you have to change it with information, analys, logic and rationality

Do you think it's logical for you to think you know what everyones needs are and that it precludes a good plate? Even when its pointed out many scrape?

on the grinding & scraping, they are not exclusive or functional duplicates. For many jobs (less than boxy), scraping one side then grinding the other is the fastest and most accurate approach to achieve flatness and parallelism. And for the man without a grinder I daresay a plate is an easier acquisition.


I was just voicing my opinion
Likewise, just a discussion, shootin the breeze...none of this upsets which I'm not always sure comes through properly in the black and white

oldtiffie
04-19-2012, 10:32 PM
Nobody here should feel or be made to feel demeaned or inadequate because he cannot or chooses not to work as any other here.

As long as that person is happy in himself with his work and aspirations it is possibly as happy with himself and/or his shop and life in general as he feels he needs to be.

Nobody should harrangue any body else by setting himself up as the bench-mark or model for any or all HSM-ers in any manner shape or form that does or might make any other feel unjustifiably inadequate.

It matters not what machines or tools he has or has not got nor how he uses them - if he chooses to use them at all.

It is totally up to him.

Its his space - leave him to it in it to do and to be as he wishes.

He will then be a contented and happy HSM-er.

uncle pete
04-19-2012, 11:32 PM
Hmmf! At least there's been some sanity thrown into this and very suprisingly it hasn't gotten locked yet. Plus I learned a few things. I'd say the OP's question has been very well answered since that cast iron surface plate just isn't cost effective to end up with a good usable surface plate as it's current condition shows. At maybe a bit less money? That plate depending on it's thickness would be worth buying just as future project material depending on your needs. I doubt you would find a better grade of cast iron, Already aged, And for sure it would have been properly stress relieved. So any project that suits that size of material might make it a pretty good buy in comparison to what you'd pay for brand new but much lesser quality cast iron plate that's standard and off the shelf today.

I don't buy anything for my shop so it's "bragging rights", I buy what works. I'm not the one posting endless pictures of apparently unused equipment along with the scans of the so called unproven accuracy specifications. I also buy what suits and works for me and could give a rats gluteous maximus if anybody else is impressed or not. I try to buy in advance and well beyond my accuracy needs of today. Just like McGyver has pointed out very well. Most if not all of us buy .0001 reading mikes because of what might be needed in the future. So apparently that's a good idea for micrometers, But somehow a few think just barely good enough is more than fine for surface plates? I dunno, As the main and central referance surface. It strikes me that it should be the one tool where you would want the very best and most accurate that you can afford.

I've read more than a bit about accuracy and scrapeing, I've also got at least two machine tools that will and do need rebuilding. I'll need to make a personal decision very soon if I'm going to do it, Or if I'm even good enough to do the work. If not, I'll pay to have it done. A good Starrett or Mitutoyo surface plate of unquestionable accuracy will allow me to make at least an educated call for some of the parts and what does and doesn't need regrinding and scrapeing, And exactly how much needs doing no matter who does the work. Very accurate referance surfaces aren't needed all the time. But when they are? A piece of scrap glass isn't going to ever get the job done. All this equipment costs good money. I can't afford to, Nor do I have the room to buy and store inaccurate, And then go buy what I should have to begin with. I've tried that route and it just isn't cost effective for me. These are my opinions and what works for me. Everyone else should just do what works for themselves.

We could all agree with each other too, Except then we'd all be wrong.

Pete