You will need to find out what kind of steel you have in order to know how to harden. If you are unable to determine the steel composition, this will work in MOST cases. First, forget the colour test. One mans "cherry red" is another mans "bright orange". IMO it takes alot of experience to harden by colour. Instead, heat it to critical heat. This is the temp where the part is no longer magnetic. Put a propane torch in a vice so you can control the part with one hand and a magnet in the other. As the part gets red, touch the magnet to it. If it sticks, pull the magnet off and continue heating. As soon as the magnet no longer sticks when you touch it, quench the part. If it's undetermined whether the steel is oil or water hardening, use a pail of room temp water with 1/8 - 1/4 inch of ATF on top. The ATF will reduce the shock that will crack oil hardening steel and the water will quench fast enough for water hardening steel. If it's air hardening.....????? I dunno. To check for hardness just run a good sharp file across it. If it hardened properly, the file will just skate across it without marking it. It will be too britle to use like this so it will need to be tempered. I would temper it like a spring which is IIRC about 650 deg. Easiest way to do that is to use a lead bath. Put some lead in a melting pot (pure lead ONLY) and put the part on top. When the lead melts, push the part into the lead (it will want to float) and remove from the heat. Let the lead cool with the part submerged. Then re-heat the lead until it melts again and take the part out and allow to cool and your done. Oh, before putting the part in the lead, soot it over a kerosene lamp of candle. The soot will prevent the lead from sticking to the part.
