quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Sept 6, 2011 22:50:42 GMT -5
I just finished slabbing fifteen pieces of obsidian for a knapper. The next to the to last piece, on the second side, gave me fits, seemed to pinch in on the blade much like timber bind in wood. Finally got through it after resetting the motor kickout a few times, but missed thickness tolerance. Is this a fairly common occurrence, or rare? It's a first for me.
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Post by jakesrocks on Sept 6, 2011 22:59:22 GMT -5
Sounds like the rock may have slightly shifted in the vise. That or a sliver of the obsidian wedged itself between the rock and blade. Check your blade. You'll probably find a drag mark on only one side.
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Post by catmandewe on Sept 7, 2011 22:15:59 GMT -5
I have had rocks close up on me before, it is not common but it has happened to me twice. Reminds me of cutting some green wood with knots that closes up on the table saw, same thing was happening but you really don't think of rocks as being able to move like that.
Tony
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Sept 8, 2011 10:47:40 GMT -5
Thanks for the comments, I know about shift in the vise and stuck slivers, didn't happen, did stick two slivers during this job. Thanks for the reinforcement about the stress movement Tony, having worked as a machinist for 40+ years, 22 of them in a sawmill, and fiddling w/wood at home, I've seen plenty of stress movement in materials; but never in rock [well, glass]. Larry
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Post by jakesrocks on Sept 8, 2011 11:50:08 GMT -5
I guess you learn something new every day. In all of my years of cutting rocks, I've never experienced stress movement in a rock. Just something else to keep an eye out for I guess. Don
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Sept 8, 2011 12:35:23 GMT -5
how thick do the knappers like it? I have a buddy getting started and I wanna gift him some slabs. Need to know how thick to send.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Sept 9, 2011 20:51:26 GMT -5
shotgunner, The gentleman wanted them 3/16". We have some modern arrowheads that measure that too. Got the saw working good at .192-.195", buyer was happy. Larry
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