# GRANITE BLOCK



## Deny1950 (Mar 31, 2013)

*Hi this might be a stupid question, but in stead of using a granite block for spreading the blue ink on a part would it be ok to use a thick plate of glass?  Would the plate glass be straight enough for that, or would it bee to slippery to spread the ink? Thanks in advance Denis*


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## Richard King (Mar 31, 2013)

I'm, not exactly sure what you asking.  I spread the ink out on any clean flat hard surface to get a even coat on my ink roller.  I have used plex-glass, sheet metal, cast iron plates, steel bars, granite table.  I could use a paint pan to ink up the roller.  But I would need a verified flat surface to ink up with my roller to rub my worn part to so I can blue up to transfer the blue that you will scrape off. I use the spec's of 0002" / in 12" for regular machine tools and .00005" / in 12" for surface plates, super precision machine tools.   I have seen people talk about using glass.  There are precision optical flats, but I have heard hardware store glass is not flat.  I have never checked it and I would find it to brittle and dangerous to use around a machine shop.  Maybe some of the other guys can add their opinion on glass.


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## Tony Wells (Mar 31, 2013)

Optical quality glass, like you might find in a good mirror is pretty flat, but not as flat as a normal good condition surface plate. As Richard said, it depends on what you want to do.. Ink a roller? Sure! Check for rub off? ehhhhh, maybe not.


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## Deny1950 (Mar 31, 2013)

What I am asking is plate glass good enough for using instead of a machinest granite slab, easier to find here rather than granite


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## Richard King (Mar 31, 2013)

If it is a hardened glass maybe, but the window pane I would say no.  But as I already stated I am no expert on it.  I can check and do some research in the next few days and let you know.


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## Tony Wells (Mar 31, 2013)

For a flatness check, I'd say no. One thing a granite surface plate has going for it is rigidity. The glass required to equate to that rigidity would probably be harder to find than granite.


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## Dr.Fiero (Apr 1, 2013)

Try and find an old commercial photocopier that's being tossed out.

The glass in those are very thick, and are obviously very flat!  Maybe not space telescope kind of flat...  But you know...  Low grade optical anyhow.  

I've got a few sheets around the shop I've had for 15 years or more!  They're pretty tough.






Sent from my iPad using Tapatalk HD


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## Richard King (Apr 1, 2013)

First we should ask what sorts of precision your trying to achieve?  Down here in the states you can buy a cheap grade B plate from Enco.  Not being familar with Canadian Supply houses.  Do you have a Enco Canada?  Every now and then I see a granite surface plate sell at auction for under a $100.00.  What size do you need and what big city or town do you live near.    I can check and see what it would cost.  There are several auctions down here in Minnesota.

I read on page 44 of the Connelly book "Machine Tool Reconditioning" and he talks about laminated glass 1 to 2" thick can be ground and lapped to .0005 to .0002" in up to 18" plates.  I will make a few calls tomorrow.  I have a good friend who is a retired optical Engineer and ask him about it.  As Tony mentioned.  I would think you would need to find stable way to mount it if it is Tempered glass and as I said before single pain glass would be dangerous and not accurate enough for most machines. .


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## Deny1950 (Apr 1, 2013)

Hi Richard thanks for the info, .001 would be good for me i think i just want to fool around with scraping, as far as enco i am only 40 miles north of the boarder and i can get stuff sent their for pic up. 18x24 would be good, i have a cross slide on my lathe that would need atention and i asked in Winnipeg Manitoba and no one seems to do any scraping here so i might have to tack one of your class and try it myself. I would not think of using any window material i was thinking on the line of say car side window or thick counter glass. Or maybe copier glass, just a thought.   Denis

- - - Updated - - -

sorry thanks also to DR Fiero


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## Richard King (Apr 1, 2013)

I did a class at Western Engine in Win about 20 yrs ago and taught several of the machinists to scrape.  The rebuild auto and train engines.  Maybe someone there could help you out.


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## Splat (Apr 1, 2013)

I wouldn't go with regular float glass which is what's sold in most hardware stores for any kind of good accuracy but that's my $.02. FWIW, I was surprised to see that granite surface plates aren't as $$ as I'd thought they'd be.  I wouldn't want to buy an expensive rock if I didn't have to though.


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## Richard King (Apr 1, 2013)

Just saw this on Amazon.com     seems like a deal to me

[h=1]Grizzly G9655 18" x 24" x 3" Granite Surface Plate, 2 Ledges[/h]by Grizzly
No reviews yet|5.0 out of 5 stars5.0 out of 5 stars5.0 out of 5 stars5.0 out of 5 stars5.0 out of 5 stars 1 customer rating for the brand




Price:*$64.95*


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## Analias (Apr 1, 2013)

.



Richard King said:


> Just saw this on Amazon.com     seems like a deal to me
> 
> *Grizzly G9655 18" x 24" x 3" Granite Surface Plate, 2 Ledges*
> 
> ...



I wonder what the shipping would be?  I suspect it's as much if not more than the $64.95 price.


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## Richard King (Apr 1, 2013)

That is an example of a super buy.  He stated he can have it shipped to someplace in the ND and drive down and get it to save on shipping, he can check with Amazon or Grizzly and also check with Enco.

PS:  I checked and Amazon to anywhere is the lower 48 is $79.00.   I also stated I see surface plates at auctions sell for $10.00, so for under $150.00 he could but a granite plate.


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## Dr.Fiero (Apr 1, 2013)

Here's the one that I bought:
http://www.busybeetools.com/products/SURFACE-PLATE-12IN.-X-18IN.-X-3IN..html

And it's only $36.99 ... and already in Canada!

As long as you can put up with it being only 12*18.


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## Tom Griffin (Apr 1, 2013)

I see these questions on the forums all the time and the answer is, granite surface plates are calibrated to a known standard, window glass is not. So the only way to know for sure is to take _the_ piece of glass you plan on using and check it to a surface plate of known flatness. If you can't do that then no, a piece of glass is not flat enough.

Tom


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## MikeH (Apr 1, 2013)

One other thing to consider with glass is its creep factor. An example of this is the distortion one usually sees in old (80+ years) window panes. Old glass was made using the float method, so it was flat and clear, without distortion. But, as glass ages, it sags under it's own weight. And this is happening with the glass setting in its strongest orientation, edgewise up (which is why glass is always stored and transported standing up). You would be using it in its weakest orientation, laying flat, so the sag would happen much, much faster. So, if it was flat enough for your purpose when you bought it, you have no reason to expect it to stay that way for any length of time.


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## Deny1950 (Apr 1, 2013)

Thanks for all the info guys At the price one can get Granite its not worth fooling around with glass. I though it was way more moula than that ,I know it wont be high end but good enough for my expertice. Thanks Denis


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## Alan Douglas (Apr 2, 2013)

Apologies, but glass does not creep or sag.  That's an old wives' tale.  (It will deflect under load, but not creep).


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