Kiridashi have an interesting history; they go way back. A quick search online uncovered one source * that traces Kiridashi and Ko knives to approximately 20,000 years ago, in Japan. These stone knives are described as using the Setouchi technique; ** making a flat stone core, which is then struck on the side to create a wide, flat flake knife, which is then retouched to create the distinctive, long, pointed knife with a cutting edge near the tip.
At some point between then and now--lets say after 500 BCE, when the iron age came to Japan--kiridashi began to be made from iron, and eventually steel. The design of the traditional steel kiridashi is appealing in its simplicity: a piece of flat stock is beveled to a point at one end, and then sharpened on one face to a keen, chisel like edge.
Kiridashi make great marking knives for woodworking--and is what they are still used for in Japan--because the flat, unsharpened edge lays tight against your straight edge or try square, taking the guess work out of where the cutting edge is relative to the straight edge you're trying to follow.
These knives can be made with simple handles, even paracord wraps, but I prefer the simple piece of steel with a sharp edge. I've seen them forged and sharpened, and ground from hardened steel, on websites and YouTube, but what caught my eye was reusing an old file. There are some great tools made from old files, and I wanted to give it a go.
A quick look around the shop this past weekend gave me two options, and both were older Nicholson files that were still in good shape, and then I found an old triangular file with the tang broken off. I almost dismissed it immediately but picked it up because it seemed to be the right length. The three sided file fell right into the sweet spot in my grip, and I knew I needed to try it.
This file is an old Simon, 8-inch regular taper (four square) single cut file, that was a little nicked up. The missing tang just made the grinding that much easier.
I ground the cutting edge on the bench grinder and I tried to align the cutting edge with the cut lines on the file (for looks.)
I ground away the back at a steep angle, similar to a chisel, but I didn't measure it.
The triangular shape fits great in the hand for cutting.
I finished the sharpening with 220 and 320 grit sandpaper on a sheet of glass. The cutting edge is sharp, keen and strong. I cut a few test lines in some well seasoned oak I have in the shop, and the marks are nice and clean. I think I'm going to enjoy working with this marking knife.
* "History of Humanity: Prehistory and the Beginnings of Civilization," edited by Sigfried J. de Laet: Unesco, Paris: 1994
** "Archaeology of East Asia: The Rise of Civilization in China," Korea and Japan: Oxbow Books, Oxford: 2015
