Now that you mention it, the collet kit I bought (the one I linked to) also came with a "calibration" blank that I've never used. That would do the trick!
Honestly I don't think you need to worry about the hardness too much. As long as it's some kind of steel, it's going to cut through ptex no problem. You just want to be able to get it nice and sharp. I shaped mine on my bench grinder, but I have a very fine grit stone. A wet diamond wheel would be better, but not needed.
Twizz 2012/2013
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