bendsum
starting to spend too much on rocks
Member since October 2008
Posts: 140
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Post by bendsum on Aug 3, 2009 2:43:30 GMT -5
My question is what grit would be best for shaping obsidian glass and possibly some flint/chert into preforms for knapping thank you
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Post by johnjsgems on Aug 3, 2009 8:48:33 GMT -5
Depends. Diamond wheels 80 works great on the flint and chert but may chip the obsidian. You might want to use a 100 or 180 if you plan on doing a lot of obsidian. It will work on the chert but slower. If you can have two wheels use 80 and 200/220. That would cover pretty much anything you would knap.
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RockyBlue
fully equipped rock polisher
Go U.K.
Member since June 2006
Posts: 1,719
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Post by RockyBlue on Aug 3, 2009 8:53:58 GMT -5
I have a 80 &220 on my grinder{green wheels} that i use for everything.
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lparker
fully equipped rock polisher
Still doing too much for being retired!
Member since March 2008
Posts: 1,202
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Post by lparker on Aug 3, 2009 8:55:23 GMT -5
Depends on the stone and your machine. A 60 grit wheel might chip obsidian. I use an 80 grit diamond wheel for preshaping, then a 220 grit wheel to smooth thing out. BTW, I rough shape on a wet tile saw - work force from Home Depot.
Lee
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Post by Woodyrock on Aug 4, 2009 0:39:55 GMT -5
Bendsum:
An eighty grit wheel will chip obsidian, a sixty will chip it worse, but take the material off quicker. If you are only using the wheel from preforming knapping blanks you might be happier with the sixty just because it is faster. I have just started knapping, and have found the eighty grit wheel builds a very nice platform....much more consistant than doing it by hand. From me, this is only about two cents worth. Woody
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