Tempering

In this case I had several small blades to do, so I hardened them at the same time as this one. Two heats and quenches each. After they were all done and cooled off, I scrubbed them all with a good grease-cutting soap and put them in the oven at 375F and left them there for about 45 minutes. I always do this before any grinding/polishing; a quenched blade at full hardness can be amazingly brittle. So I give them a heat at a temp low enough to take the very edge of hardness off but not go beyond that point.

After that time I set them out to cool. Once cool I hit them with the belt sander to clean and shine up the surface. Then back into the oven at 375 again. Yeah, I just did that. Just in case the thermostat is off a bit I give them that heat again for 30 minutes. Note that these are small blades, for large and/or thick ones I'd give them a full hour. Then pull them out and check the color. It looks like it should, a barely-there yellow on these steels, I up the temp to 400 and put them back in for a half hour. With these blades that generally gets them where I want.

This is about the best I could get to show what I like for a blade like this, a medium to dark bronze color. With this steel that is hard enough to hold an edge well in use, not hard enough to chip or crack in use and not a big pain to sharpen












It depends, of course, on the use. Something like a throwing knife you'd want to temper down a lot more to a spring, probably somewhere around 450-500 and a dark purple/light blue(again, depending on steel). Something for fine cutting you want to stay sharp and don't mind taking time to touch up when it dulls, you can leave some at 375 for the temperature.

In any case, after the first full temp heat you set it out until it cools to ambient temperature, then back in the oven. Repeat until it's had three heating/cooling cycles at the chosen temperature, and after the last just turn the oven off and leave it in there until cold.

That should get the blade to a nice, even hardness.