Chisel Tempering

This is a 1/8-inch chisel made from music wire. To begin, I cut a 6-inch length using a high-speed rotary tool and cut-off disk. I heated the blank to glowing red and let it cool slowly (annealing). Then, I was able to shape it with ordinary files. I shaped it to half thickness for a few inches on one end (half-round cross section), with a bevel tapering from the round side to the end.

After shaping, I heated the working end to glowing red with a torch and plunged it into a can of oil. I polished the flat surface and slowly heated it over a gas flame until it turned a deep straw-bronze color (tempering). You can see some purples and blues toward the left (handle) side in the photo. The steel is softer there, which is fine, because you don't want it to be brittle.

Actually, I messed up the temper the first time, and had to heat treat it again. Fortunately, you can do that!