Primitive Archer
Main Discussion Area => Flintknapping => Topic started by: Knocker on March 31, 2010, 02:53:49 am
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Hey Guys,
Trying to cut some slabs for the first time - Glass Butte obsidian. I'm afraid I might be making them too thick. Is there a rule of thumb for thickness? Does the length x width of the slab figure into it, or is it based on what you are trying to create?
Thanks,
Knocker
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if your pressure flaking yes the width does matter. Your flake has to be able to run at least to the middle. As for percussion 5/8 is a common thickness, thats all I have ever cut my rock for is the percussion thickness
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Keith,
Have you tried any of the slabs I gave you? I usually cut my slabs at 1/4 inch to 3/8 inch. The widest I make the blades are as far as I can run a flake to the middle. If you need any help PM me and I will Tell you my phone # and we can talk.
Tell
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I usually cut my slabs according to the width they are coming off the rock. If it is not more than 1.5 " w then 1/4 to 5/16 as a slab get wider it becomes more of a percussion slab and will get thicker. 2 -3 inches wide 7/16ths to 1/2 thick and if they are 4 or more wide, 5/8ths and even more if they are really large, up to an inch or more.
Steve
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Thanks Tell and Steve... Increasing the thickness with width makes sense to me. I think for most of the slabs I am making now, that I just want to work on arrowheads and small knives or spearheads, so even if they could be larger slabs, I might make them 1/4 to 3/8 thick and resaw the slabs into smaller pieces for pressure flaking. I've got some dacite I can always practice percussion on.
Keith
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Keith,
What are you using for a saw?
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Brian - I am using a 16" diamond blade saw with a screw drive rock clamp. I'll probably spend the day tomorrow cutting slabs.
Keith
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just throwing this out there
i like slabs of obsidion ::) ;)
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Keith,
If you want slabs that are all the same just block a piece out and then slice it like a loaf of bread. then they will all be consistent size. I don't always cut them random size like I posted earlier. That depends on what rock I am cutting also. If it is more rare material I usually cut them random as they come off the rock, if it is more common material like obsidian I will block them sometimes and cut them consistently. But I usually cut as large a block as I can and will snap individual slabs from larger ones with a tile cutter.
steve
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Keith a lapidary saw, or something you made, got a pic?
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Brian - Here is the saw I am using...
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It amazes me how different some of this Obsidian looks with backlighting. Look at these pairs...
The last one has a beautiful gold sheen, but I have no idea how to photograph it.
Keith
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Dang Keith. Looks like you have lots to knap now. You really picked up some nice rock.
Tell
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Happy Easter Tell! And all the rest on PA as well! Yeah, the plan is to get it all cut up while the wind is howling and the rain/sleet/snow is rattling the tarp. Hopefully my knapping skill will take a jump when it warms up enough to set a stool out next to the saw...
Keith
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Man that is some beautiful rock,
Steve
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Looks home made keith where did you get that at?? What did ya have to give?? I sold a 20 inch saw for $1650 last week. ;D
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Brian - Yeah, it's homemade, and I think who ever did it did a great job. The only thing I could wish for is the ability to gear up the drive a bit. It is only cutting at a 1/2" per minute. It would be nice if you had a two speed for hard and soft rocks. The price is the best I could ask for - I am borrowing it for free. It belongs to my neighbor who hasn't used it for years. He said he paid $50 for it... Think I should offer to double his investment???!!!! >:D
Keith
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Yep I would jump on it! Bet you could figure the gearing problem out. ;D