Hand Tools Archive

Subject:
second unicorn edge retention test

David Weaver
This time, I used apple for a specific reason - I have an offcut just under 3/4ths inch wide, which means I can use the sorby chisels to cut it without holding wood on the side.

First test, same chisels (unicorn 1 inch, 28 degree 3/4ths inch) using the edges shown in the angle pictures (not resharpened, etc). flat bevel is 1 micron diamond, unicorn is yellow stuff.

83 strikes to get the flat bevel chisel through the apple, 60 to get the unicorn chisel through the apple:

edge damage to the flat bevel - 3/4 inch sorby:

This apple feels a little bit harder and drier if that makes sense vs. the beech billet. The edge failure is much more uniform in it. If you check this chisel with your finger, it feels like a wire edge has been raised (a small one, but you can easily feel it.)

1 inch chisel - unicorn edge. No visible damage. It's hard not to tap the mallet more lightly even from the start as it gets through the wood much more easily.

Next, swap the chisels, unicorn the 3/4th chisel and flat bevel on the 1 inch chisel to make sure it's not the chisels and lack of consistency. (i've never perceived much variance in three sets of these chisels, but you have to check and make sure it's not also related to a bigger chisel transferring more of the mallet energy).

80 strikes with the flat bevel, 55 with the unicorn. I paid a little bit more attention to not let off of the striking pressure since the unicorn was getting through the wood more easily.

28 degree bevel, 1 inch chisel:

Then, the 3/4th inch chisel unicorned:

I'm not sure if any of that is minor edge damage.

I drew 10 sections in each inch of malleting here. Again, wood narrower than the chisel width so no holding wood.

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