I’ve been working on a knife using a process that does not require forging into shape, rather to get it into shape I used the process called profiling. This is when I cut the shape of a knife out of a flat piece of metal. I had bought an old file at a yard sale for a nickel, and so I used this for my knife. (It is fairly good quality, as it has to be hard enough to file steel)
First, I annealed the file (which means softening the metal so it will be easier to work) by heating it up with a blowtorch, monitoring the metal’s heat with a magnet. Once it gets to the desired heat (an orange-red color); the point at which the atoms are able to rearrange, the magnet will no longer be attracted to the metal, and at that point I stopped the blowtorch and just put down the metal to cool slowly. This is so that at the annealing temperature (the point where the magnet stopped sticking), the atoms are able to rearrange themselves in a nice “agreeable” pattern by the time it is completely cooled down.
Once it was annealed, I went online and found a printable knife template, which I printed out and glued to one side of the file. With a combination of an angle grinder and a file, I cut out the exact profile of the knife (though later I sloped down the point a little further). Then, I clamped down the knife so the edge would be facing myself. This I slowly filed down (man, even with the metal annealed, that took a while) on both sides, ’till they sloped down and met in the middle. I did not sharpen it, however, as later on the processes would bang up the edge, and that would mean a lot more filing. Anyway, with the profile of the knife complete, and the edge ready to be sharpened, I moved onto hardening and tempering the blade.
For this part, I actually left the paper and glue on, as they were about to be incinerated anyway. I began heating up the blade, (though not the handle, as there was no need to harden it) slowly monitoring the blade with a magnet until it got to annealing temperature. At this temperature the atoms are out of place and moving around. Instead of just leaving the blade to cool, this time it is much more fun. I picked it up with tongs and plunged it into a bucket of water I had nearby. Lots of steam, awesome hissing. When I did that, all the atoms, which were out of place, became locked into those positions. This made the knife hard and brittle. To test out that the hardening worked correctly, I ran a file along the blade and along the handle. On the handle, it made a low-pitched sound, cr-ggghhhh, and a large mark. On the blade, it made a high-pitched sound, ssshhhhiiiiiinnnngg!, and a hardly visible teensy-tiny mark. The blade was hard, but very brittle. Too brittle. Which meant it had to be tempered.
Tempering a blade is softening part of an already hardened blade so it does not snap or chip. However, we do not want to temper the edge of the blade or the point, as tempering them would later on result in denting and very quick blunting. So, I only tempered the spine, or back of the blade. To begin, I sanded off all the firescale (oxidization caused by the heating from when I hardened the blade) from the blade, you’ll see why.
Anyway, I began slowly and carefully heating up the back of the blade, staying away from the edge and point. Have you ever seen metal, when it begins to heat up, and a sort of blue color spreads across? I waited until the blue has spread from the back of the blade until little more than halfway towards the edge and then I quenched it. The areas where the blue colors are are a certain temperature, and it is at that temperature that the atoms loose up from their very tight fitting just enough to effectively soften it. Then the quenching locks that in place. The edge and point however, remain untouched and unaffected.
After I had done this I sanded off the accumulated firescale, and sanded off the blade further, making it nice and shiny. I then drilled two holes in the handle for fixture of the wood. I’m not sharpening it yet, as the handle still needs to be assembled. I’ll post about that once it’s finished.