This is a follow-up to a previous post. Earlier, I mentioned a knife blade that I had forged and was preparing for heat-treating (hardening).
The knife was given a clay resist along the back and also at the end of the tang. The clay prevents whatever area that it is coated with from becoming hard during the heat-treating process. Of course, a watchful eye on the temperature of the knife while it is heating is essential. A few degrees too cold and the knife will not become hard. A few degrees too hot and the clay will not function properly. Or worse, if the temperature gets far too hot, the knife will be brittle.
Making steel hard is always exciting for me. The knife is heated until it glows a bright red and is immediately placed into hot oil. Once the knife is removed from the oil bath, the oxides that formed on the surface flake off as the steel reaches room temperature (due to the shrinking of the steel and the growth of the martensite structure). The white areas are where the oxides (scale) has come off. It is also the first strong glimpse into what pattern will be visible on the finished blade.
Remember that the metal is pattern-welded? It is a basic ladder-pattern. Because it is only about 42 layers, the pattern is pretty bold.
It is crucial that the tempering be done as soon as the knife is cool enough to touch. Although the picture does not show this clearly, the tip and edge have a pale yellow cast.
Because my heat-treating was what I would describe as “optimum”, I need to be careful to not get the steel too hot while I grind it to its final shape. A file bites easily into the area along the back (where the clay was) and only just barely bites into the area along the edge. Because the back of the knife is so soft, I can get away with having the edge be a little harder than might be normally expected.
After some judicious sanding and finishing with stones, the knife was really beginning to take shape.
I had a beautiful piece of Bois de Rose that I was eager to use. I wanted this knife to have a partial tang (so it would not conflict with the beautiful wood), yet be substantial enough to withstand any use that the knife would be subjected to.
Along the way, I decided to make a sheath as well. Overall, I am quite pleased with the result. The lump of metal that was on my shop floor finally got to fulfill its potential and I was able to share this with you.
The recipient of this seemed quite pleased as well.