Tools and Surface Plate Questions

If you buy a used surface plate, you have an unknown. You are not likely to be able to check it with any reliability by yourself in your home shop. Buying a used plate by brand name and paying more for it is about the silliest thing I can imagine. They are all chunks of rock that look visually flat. I bought my 18x24x4", 2 ledge for $50 off a rack behind a machine shop, covered with junk and grime. I "guessed" it was in pretty good shape by chasing various indicator setups and straightedges around it and scratching my head. A group of local hobby machinists brought their plates to my shop and Standridge granite dropped by to calibrate the 5 plates. Mine ended up costing ~$103 to be calibrated to AA grade and certified to A grade. It turned out to have a .003" "hole" in the center. To be used for precision work, guessing will not do. A friend bought a very nice pristine looking 24x36" Starrett pink plate for a pretty high price, and it turned out to have a .005" hole in it, and had to be taken 400+ miles to Standridge's facility in SoCal to get it calibrated, they will not remove that much in the field. IF THE PLATE HAS NOT BEEN IN YOUR POSSESSION AND UNDER YOUR CONTROL SINCE IT HAS LAST BEEN CALIBRATED, IT IS NOT A SURFACE PLATE, IT IS "AN UNKNOWN KINDA' FLAT LOOKING ROCK." No exceptions. The idea of a surface plate is it being a known flat plane reference surface in your shop. If it is not a known quantity, it is worthless for that job. If you want to use it only for simple layout work or for lapping non critical parts, stacking parts and tools on, eating your lunch, a tombstone, or some other non precision use, then go for it. Just don't hope that it is something it is not.
 
Do you mean the 9 X 12 from Lee Valley? I don't remember them ever selling a larger 18 X 12, but if they did I should have bought it. The 9 x12 is a nice surface indeed a bit tight for anything bigger than a few inches square.

-frank

Yes, sorry. It was some time ago. The plate was very good however.


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Bob is extremely knowledgeable and operates to a tolerance much higher than I. While I don’t have the entire chain of custody clearly mapped for my Starrett 24 x 36, my point was to say, buy the biggest that you can afford (cost and space limiting). Further that for the hobby Machinist, most surface plates, morsels of granite from counter top shops or even plate glass will suffice. If you are building the space shuttle replacement along side Bob then finding a hole .003 deep could be a problem..... I on the other hand am ok with that as a tolerance. All with a grain of salt....


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so I'm considering a 12x18 size plate. I can pick up locally a grade-B Standridge surface plate via McMaster Carr

I use a 12 x 18 pink surface plate (Starrett) and I've been frustrated only a few times in 20 or so years of use. It fits nicely on a Kennedy roll around that is dedicated to the job. I got it with the factory offered cover and also have an additional layer of padding under the cover.
291038

The height gage is a Swiss Etalon of about the same vintage. It's 18" high and I've appreciated the height a few times. The surface gage on the left is a Starrett and the stubby one on the right is shop made.

The most important tools in the drawers are two nice sets of Jo Blocks which I use A LOT. Also, various other measuring and layout tools as you would expect.

(And, for you guys in Hawaii, that's two feet of snow outside the window...)

MetaKey
 
Bob is extremely knowledgeable and operates to a tolerance much higher than I. While I don’t have the entire chain of custody clearly mapped for my Starrett 24 x 36, my point was to say, buy the biggest that you can afford (cost and space limiting). Further that for the hobby Machinist, most surface plates, morsels of granite from counter top shops or even plate glass will suffice. If you are building the space shuttle replacement along side Bob then finding a hole .003 deep could be a problem..... I on the other hand am ok with that as a tolerance. All with a grain of salt....


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My post was directed to all those reading this thread who might be considering purchasing a surface plate, Moderatedmixed, not directed toward you personally or your posts here at all. I have seen many here and elsewhere who seem to have incorrect (in my mind) ideas about purchasing used surface plates. When buying one used, we have no idea how it might have been used or cared for. That was (and is) my message. I am just another hobby machinist who cares to understand what I think I know, what I don't know, and how it affects my results. I do the best I can with what I have, as do we all. Much of the work in my shop is pretty crude.
 
(And, for you guys in Hawaii, that's two feet of snow outside the window...)

Yeah, I noticed that right away! Alas, it's 79 degrees here and not a snow flake in sight ...

Nice set up you have there, by the way. I'll have to look for a dual column Etalon - never knew they made them!
 
I bought an 18x24 grade B from Shars with their steel stand. The stand supports the rock in three places. I don't work on large parts but I wouldn't get a smaller plate. I have no way of checking the trueness of the plate other than my gage blocks and dial test indicator, and moving about the surface plate I haven't been able to detect any variations. This is of course a very limited method because it is only comparing areas that are relatively close to each other. I also have a, less than ideal, import, dial ht. gage. Used for "close enough" ht. measurements and scribing layout lines. The two have very different uses so I would guess both are needed by most people.
 
I have an 18X24 Mit AA grade plate, and it seems perfect size for all the work I do, and some of it gets near to being too big, but so far, it has sufficed. I do know of a shop I can work at that has a Mit A grade 36X48 I can use for the really big stuff.
 
I have a 18x24 and it gets tight on some things. Blueing up parts eats up space quick. Then swinging gauges aroundfeels like I’m always on the edges of the plate. I’d go for the biggest you can afford. Shipping is a killer thankfully Im close enough to pickup than deliver. I use 12x18 cast iron ones for simple scribe and layout work near the machines, auction purchases.
 
For something as heavy as a surface plate, check with McMaster-Carr on shipping cost before you order. I got stuck with a $69 freight charge on a 1"x10' $7 PVC pipe from them because it was over 8 feet. Anything that exceeds FEDEX or UPS "limits" goes "$$$ freight $$$". :(

Ken
 
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