Tools: Marking knives

May 20, 2008

Before I knew better, I bought a nice Japanese marking knife (bottom, in the photo) for something like $13. Don’t get me wrong, it’s a nice piece of steel.

But I later made one that was functionally equivalent out of an old Dewalt reciprocating saw blade that was otherwise ready to be thrown out. I filed the teeth down a bit, which were pretty dull by then anyway, and they made a nice no-slip sort of grip (top in the photo). Both of these served as well as I could ask, except in the case of very narrow dovetail sockets, which require a very thin-bladed knife.

Marking out pins from dovetail sockets also works best with a knife that has a single angle and is beveled on just one side, as opposed to one ground to a point or beveled on both sides. You stand the knife against one side of the socket, the point of the blade reaching all the way back to the inside edge of the pin stock, and scribe across the endgrain of the pin stock, carefully keeping the knife steady against one side of the socket. The knife has to pass all the way across the pin stock. With narrow dovetail sockets, sometimes the narrower ends of the sockets are barely wider than the kerf of my dozuki saw. But the knife has to slide through that opening so you can scribe all the way across the thickness of the pin stock. That’s the first thing I wanted: very thin metal for the blade.

But to mark both sides of the socket you need two knives, really, mirror opposites. That’s the second thing I wanted: mirror opposite blades attached to the same tool, so I wouldn’t have to change tools. So that’s why I made another marking knife, two pieces of very thin steel, cut from an old card scraper, and a little piece of boxwood as a handle (middle in photo above; and by itself below). Works great. I mark all the sockets on one side, then flip the knife over and mark the other sides.

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