Heat Treating Knives

Before heat treating you want to normalize your blade to remove any stresses that may have appeared in forging. You normalize your blade by brining it up to non-magnetic and letting it air cool. Some people do this 3 times just to be sure that all the crystals have become the same size and that the blade is fairly soft. I'm not sure I can tell the difference between one cycle and three so do what you are comfortable with.

Heat treating is a 2 step process. The first is hardening and the second is tempering. Start with a normalized blade (heated to non magnetic and air cooled.) Heat the blade until its non magnetic. Test with a telescopic pen magnet if it doesn't stick it's ready to go. Then quench it in motor oil, canola oil, olive oil whatever works  which should been pre heated to about 125 degrees Fahrenheit. If it's single edged then quenching it in a pan edge first would be best if it's double edged or 2 long for a pan then quenching it tip first will be fine. (I usually just plunge it all the way into the oil tip first. Do not wave or stir the blade in the oil as this can cause warping. I let the blade air cool I have known others who will water quench it after the oil quench. After that clean the baked on oil off of the blade then you can draw temper. The use of the blade depends on how hard you want the edge. You can do a differential temper by feathering a torch along the back of the blade until the edge turns light straw colored this is the hardest an edge can be with out over stressing the steel. The colors are straw, light yellow, yellow, light brown, dark brown, red, purple, blue, gunmetal gray. Straw is the hardest and Gunmetal gray is the softest and ideal for the back of the blade. If this is going to be a chopping/camp knife I would use a light brown for the edge. If it's going to be doing a lot of slicing like a kitchen knife then straw is fine for the edge. You can also put it in the oven for about 2 hours at 425 to get a straw. The colors start changing about every 10 degrees if I recall. I have the temp to color list someplace and will look it up and post it if it is useful to anyone. You should use the oven draw for double edged blades.