GRANITE BLOCK

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Deny1950

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






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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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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

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sorry thanks also to DR Fiero
 
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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