Wikipedia says "Gauge plate is a special kind of carbon steel, manufactured to exact dimensions, and delivered in annealed state. It can be hardened by heating to a specific temperature, the Curie point, and quenching in water or oil."
Does that mean heat it until it's no longer magnetic (perhaps easy to test for using a magnet - as long as the magnet has a higher Curie point, I suppose)?
The stuff I have says "oil hardening" on the outside, but what sort of oil should I use?
Is it like silver steel, which I have hardened - does it then need tempering? I want it as hard as is compatible with use as tooling, think eg a mill clamp set or tee-nut, something like that.
As I said, any tips welcomed. Thanks,
-- Peter Fairbrother