If anyone REALLY wants to know more about tempering, etc, see if you can find a book called The Making of Tools, by Alexander Weygers - he wrote a couple more, I have 'em somewhere but don't recall the titles exactly.
Weygers is (was, maybe) actually a sculptor, who ended up traveling worldwide - he describes things like being given a piece of exotic wood, "seeing" the animal inside, as sculptors tend to say, then realizing he wasn't home, had no tools, yadayada - he then describes finding (for example) a couple worn-out files, meeting a man and his son who had a makeshift forge, forging the sculpting tools he needed, then a pic of the finished piece, etc.
It's a very entertaining read as well as a learning experience - the title I mentioned even has a full color chart of oxidation temps/colors, as viewed in a dim light - VERY useful in tempering/hardening.
It's usually a pretty hard to find book, but well worth the effort IMHO... Steve
