Many years ago, my brother in law, who was a mechanical engineer /
toolmaker, gave me a bag of 'case hardening powder', which I still have.
Does anyone know what exactly this stuff is (it's white, and if the police
got hold of it, I'd probably be locked up whilst they determined just what
it was ...) and how to use it ? I got to thinking about it today, when I was
stoning the edge on a chisel ready for use tomorrow on a job. It occurred to
me that once the original factory edge has gone from a wood chisel or plane
blade or whatever, and you've resharpened it, it never seems to last as long
again as it originally did. Is this because they harden the edge when it's
made ? Is it appropriate, or even possible with home DIY facilities, to
harden the edge once it's been restored ?

Arfa