As the title, just a good read with a lot of info.
http://niftydeluxe.com/crookedknife/CrookedKnife.htm
http://niftydeluxe.com/crookedknife/CrookedKnife.htm
Be careful of this article, where the author writes
(1) Anneal the file to soften the steel so that it can be worked. This is done by heating it to a cherry red color (about 1250 degrees F) and quenching it in water. A propane torch will generate enough heat.
He is doing the opposite. The result will be an extremely hard brittle file. It will be almost impossible to shape and if dropped, it is likely to break.
To anneal, heat it to cherry, then let it cool as slowly as possible. Traditionally it would be put in ash to do so, today Vermiculite is great.
m.f.