Hand Tools Archive

Unicorning other steel

Bill Tindall, E.Tn.
I have a table/buffet underway and about to dovetail the drawer dividers and blades into the blades and legs respectively (English terminology , I think). Seemed a propitious moment to prepare the chisels for this task with a Unicorn Profile.

Hollow ground at 25 degrees, less than the 28-30 normally used. Refined bevel with fine fixed diamond stone followed by 1 micron diamond on cast iron front and back. I may get there but for now I am not seeing any advantage for the multi angle bevels David advocates. After hollow grinding it is but seconds on the two diamond formats. Finally a 2-3 second pass across a 3600 rpm 6" wheel with 5 micron "yellow" compound.

One chisel is made from CPM 3V, an exceptionally abrasion resistant steel due to the 3% vanadium which forms one of the hardest carbides of any metal but tungsten. The other steel is PMV11.

Both chisels displayed the thin bright band at the tip, indicative of the Unicorn Profile. As best I could tell with out a microscope the two steels behaved equivalent on the buffer.

It has gotten late. Tomorrow AM they will be put to use.

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