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Ptychodus04

If you go slow and regularly cool the chisel, you could do this to a regular cold chisel with a grinding wheel. Clamp your chisel in a vise and start grinding. Stop every 30-45 seconds and dunk the chisel in some water and you shouldn't ruin your temper.

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Sagebrush Steve
20 hours ago, BobWill said:

A few years ago at a rock quarry north of Abilene TX I was told about a great way to cut limestone when it is quite a bit harder than the usual chalky stuff. Whenever your fossil is in a huge rock and you need to go in after it most of us don't carry a portable saw along so a hammer and chisel is the next best thing. Adam A. showed me a chisel with a blade like this:

 

WIN_20190615_21_56_32_Pro.jpg.715b5ee5151cc7db4aa1a34a042ba54a.jpg

 

They cut rock quicker than a flat blade.The notches in the blade seem to make a big difference, maybe because they are taking off smaller chunks on each strike. This chisel is 9” X 5/8” or about 228mm X 15mm.

 

I found it at a company who makes them for carving marble so they are good quality. They seem a bit pricey but you would probably spend the same if you bought a cold chisel and had a machine shop cut the notches. They would also have to re-temper it for you. If you have the equipment to do this to an existing chisel yourself all you spend is some time so let me know if you do. See if it cuts better than a flat blade.

 

I found mine at Trow & Holden. On their website click on: Shop Online, Steel Hand Tools, then Steel Marble Hand Chisels. They have several tooth patterns. This is “H” and it's what I was shown at the quarry but I haven't tried the others. Some are clearly meant for sculpting.

Makes sense.  When you hit it, the same amount of force is being applied across a smaller area so the pounds per square inch is higher.  And it is being applied across a longer length than if you just used one smaller chisel.  (Sorry for the engineering analysis!).  I wonder how it would work on softer shale?  Maybe not as well?

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BobWill
2 hours ago, Sagebrush Steve said:

Makes sense.  When you hit it, the same amount of force is being applied across a smaller area so the pounds per square inch is higher.  And it is being applied across a longer length than if you just used one smaller chisel.  (Sorry for the engineering analysis!).  I wonder how it would work on softer shale?  Maybe not as well?

The engineering analysis just confirms my instincts so that's a good thing. As for shale I  think there would be a disadvantage to a notched blade. I think most of us would use a thinner, wider blade for that so that leaves us with a heavier but more effective  tool box.

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erose

Reminds of using a star drill to bore holes in rock.

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