I (vaguely) remember someone in my school (as a pupil) metal working
days making a mini-vice and case hardening the jaws - or more exactly
We case-hardened other things, a standard project was an adjustable
wrench (I still have mine). We used a black powder- I assume carbon
based- heated the steal to red I think, buried in in the powder, left
it, then clean it off when cool. I don't recall a tempering stage- but
it was near on 45 years or so ago.
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