Monday, April 10, 2017

Small belt knife

This is my new personal knife - and, insofar as I "need" one (only for small tasks like opening and cutting up boxes), likely the only one I'll ever need outside the kitchen or art projects.

It's made to an 18th-century Scottish aesthetic to go with some of my other projects, scaled down to the size of what we would now call a patch knife*.  The blade geometry isn't correct for the 18th century, since it's a modern Lauri blade from Finland, but this was the best I could find in a bare blade without going custom.  (Judging from every photo I've ever seen, real 18th-century knives had a triangular "backed" cross section.)  Specifically, it's the 80mm Lauri stainless blade distributed in the U.S. by Ragnar Forge.  This is a heavy blade for its size at roughly 1/8 inch thick, designed for whittling and general work.

I modified the blade, grinding the tang upward on the edge side and the spine down a bit on the back, so the tang is off-center and the blade has a little shoulder.  Also, it transitions to slightly rounded at the very base so as not to leave any corners sticking out where it meets the ferrule.  Lastly, of course, the traditional jimping which is supposed to add grip when pinching the spine to work on delicate tasks.

The blade came with mirror polish but also a faint ribbed surface which I assume resulted from the initial factory grind.  I sanded and polished it to a near-satin finish that didn't quite manage to get rid of the ribbing, but obscured it somewhat.

The ferrule is a copper plumbing end cap.  These are made circular with slightly rounded ends, but annealing and a few minutes with a hammer give it a roughly oval cross section and flat top.  More challenging was the brass plating.  The old lye-zinc trick, used to give pennies a zinc plating which is then heated to fuse with the copper coin and produce a yellow brass coating, only produced any significant deposition on the spots where the ferrule was in direct contact with the zinc dust.  Worked great on a penny I, though.  I theorize this process doesn't really work except on thin, flat objects.  (Also I had a bit of a cough after the attempt; maybe the lye fumes hurt my throat?)

What worked better was electroplating, using two AAA batteries in a battery holder and a much more benign mixture of zinc, vinegar, sugar and epsom salt in a one-quart plastic yogurt carton.  The ferrule plated in seconds, polished up to a nice silver and produced a solid brass finish when heated.

The grip is American walnut with linseed oil.  I threaded the tang and ground down a brass hex nut to secure it, and assembled with epoxy for good measure.  Lastly, the sheath is good old vegetable-tanned leather, though a bit lumpy because I'm not very good at skiving, dyed brown and polished with shoe wax.  It fitted loose, but I shrank it with soaking and judicious warming over a heater (which I understand can ruin a sheath if done to excess - thankfully in this case it worked out.)

* A number of Scottish knives are preserved that resemble a mashup between a Highland dirk and a chef's knife, typically having a triangular blade and hafted with antler or carved wood, as on one thought to have been recovered from the field of Culloden.  These are sometimes identified today with the knife referred to in literature as a sgian achlais.

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