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Mittwoch, 7. November 2012

Another day in the smithy-some musings on steel qualities and how to forge a Tai - Goo - style bush knife..

 On Tuesday, Istopped by the Bethaus smithy do do some projects for myself. First and foremostly, I had that urge again to do another bush knife;-), but I also tempered the leaf handled Kopis knife I made on Sunday, and a Nessmuk design knife with a flat tang. Then I took the uppermost piece of spring steel and set out to forge a hollow tang bush knife after Tai Goo.
 First I forged the blade part and set it to be about half the width of the handle part. A tip was then forged.
 Then the tang part was flattened, and, with the help of a hardy device, rolled onto itself. You can also use a vice with the jaws slightly apart. Use the peen of the hammer to do the preform. Then you can use the anvil´s surface to roll it onto itself. Be careful to execute the same number of blows on both sides.
 Then the blade was forged, and at the end of the handle a hook was formed to prevent a wrapping from sliding off, the handle being not conical. The blade itself was forged to edge. This knife was already ready to use after forging with no stock removal, and no, I am NOT going to tell you how I did it;-). There was clay involved, so much I can say;-).
The knife will get a ground edge surface, though, to enhance the geometry and get rid of some irregularities in the edge line, though. The blade has a selective temper.

Now to the steel: I find I use spring steel ever more often, in fact, I realize that there is all you need in this steel for bushcraft and hard use applications. It simply works. I have thought about that. The spring steel I use ranges from a carbon content between 0,55-0,80%, with manganese and slicium in the alloy, making it tougher, and maybe one or the other Chromium atom. It´s nothing compared to highly alloyed steels that are all the rage in the knifemaking world. D2 is an example I love to use to illustrate the fact. Known in Germany under the material cipher 1.2379, it is most commonly referred to as "tool steel", and most commonly used for stamping tools and cold and warm chisel tools. As the saying goes for knives out of that material, "they take a lousy edge but hold it forever". The high degree of alloy in this steel makes for vast carbides, nearly visible to the naked eye and resulting in a more coarse edge, almost like micro - serrations. For a hunting knife, this might even be an advantage, but for a bushcraft knife you want a fine edge. Woodcarving requires a polished edge surface to make controlled, powerful cuts manageable in a better way.

Spring steel, which is alloyed with Silicium, which, generally spoken, delivers a higher ductile strength and a higher flexibility, and manganese, which is also responsible for a higher flexibility and contributes to even out the carbides in the steel, is, while offering a tempering potential up to 61 degrees Rockwell after annealing, higly flexible, and makes, when treated the right way, for quite a tough blade. Plus, it is dead cheap and widely available. I really put my blades through their paces, and I hope one day they might pass the ABA test. I have worked with some fancy materials, and I get them to work quite often, even tested hard. But in an equation, I tend to return to spring steel more often than not, for, honestly, a knife has to be reliable and serviceable, especially in the woods.

For that, I have come to love those bush knives. They are dead simple, and that means little can go awry with them. No scales to come loose, no handle either, and you can even cover them up with makeshift cordage. They are widely used by indigenous cultures for a reason. You can use them for knife throwing or fit a stick into the hollow handle to make a spear. I have even harvested wild apples and plums and maple blossom that way. I already tested the knife some, for I was being curious, and it supports my weight when stuck in a wooden pole, and that´s a feat;-). A think a thorough test will follow soon...*ggg*
Try that with a 64 HRC D2 blade*ggg*.

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