Preparing a granite surface plate

Hmmmmm....
That is exactly what I was suspecting. A new plate was probably fairly well cleaned after manufacturing but there must be still some dust, particles and whatnot on it.
So this has to go somehow. I did not know about using amonia on granite.

Also while on the subject, a 'B toolroom grade" plate is surfaced to 0,0002" which is is about twenty times better than my abbility at machining right now! I will buy one from a machine tool distributor, I 'need' the comfort of buying something certified, but just out of curiosity, how flat are the granite found at countertop or toombstone fabricator ?
Also, again out of curiosity, I had some belgian, french and austrian colleagues at one point or another in my career and contrary to us north-american as where we refer to a 'surface plate, or a 'granite', they refered to a 'marble plate' or simply a 'marble'
Is it just because granite is more common in America, and marble more comon in Europe, or this is just a semantic quirp?

Luc
I can’t say for tombstone, but i have checked countertop granite- it failed when blued up on my A plate
It’s better than the garage floor but not precision by any stretch .
 
My dad was an artisan bookbinder and I remember as a kid he had this big piece of granite from a friend who made tombstone, monument bases, and that sort of things, hence the question! :)
That stone was used as a surface where one operation required that the book spine be hammered to give it the roundness.
Just hamering on a bench, no matter how sturdy it was built, did not produce the required results.
 
I tried the "piece of countertop" option first and found it to be within .003. It was
small however and when I got a piece that was 14" x 14" the error was "bad" to say the least. I paid $250 for a Starrett 24 x 36 x 4 on Kijiji (Craigs List for Canadians). If you are a bit patient you can get a "name brand" for a decent price. That said, a buddy has a 12 x 18 "Chinese" plate and it is as accurate as my Starrett. (.0005 over 18 inches). I think marble was used because of a lack of granite overseas (rampant speculation). Good luck..... let us know what you end up with.


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While watching some Vintage Machinery videos on YouTube. Richard King advised the guys in the class to use windex. I have Starrett surface plate and it seems to work well.
I have used Windex (well, actually generic cheap Windex substitutes) and it is a great and cheap cleaner for surface plates and for scraping cleanup. The downside is that some of it causes iron and steel to rust pretty badly and quickly. BTW, the water soluble Canode spotting inks will also cause corrosion if you leave them on your parts or tools.
 
That said, a buddy has a 12 x 18 "Chinese" plate and it is as accurate as my Starrett. (.0005 over 18 inches).
.0005 is not accurate enough for a 12x18" surface plate. On a 18x24 the entire surface should be within .00015 for a grade A plate of that size. Names like Starrett mean nothing on a used surface plate, and there is no reasonable substitute for having your plate professionally inspected and calibrated so you know what you actually have. Anything else is guessing and hoping. Shiny does not mean flat. Small dings do not compromise the flatness.
 
Bob..... I missed a zero. But thank you for correcting me as you seem to do so for everyone, I feel honoured.


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Back to Old Carl here. (The Tool & Die Maker that I first worked with and should have paid better attention to...)
Back to work after the two week summer shutdown, he was removing the cover from the surface plate in the shop
and asked if there was any coffee left in the pot. (I had brought in a Bunn-O-Matic when I first started there.)
'Sure' says I, and he asked me to fetch it. He then proceeded to use the coffee, black, no cream, to clean the surface plate.
 
i agree, simple green will not compromise granine either,
but simple green can leave residue that doesn't flash off

fretting over, protecting and cleaning a piece of flat rock would be considered heresy by any other profession or pastime
 
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Bob..... I missed a zero. But thank you for correcting me as you seem to do so for everyone, I feel honoured.


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You are quite welcome, and I hope you and others will return the favor whenever I or anyone else spreads information that may be incorrect. We are all learning here, and incorrect information does not help anyone. I really want to be part of the solution and not part of the problem, so please let me know when I am mistaken or out of line.
 
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