Thread: DC style marking knives

A couple of years ago, Derek Cohen gave me one of his splendid little marking knives as a token of friendship. He didn't know it at the time, but I had seen & liked his design, & already made a similar one (imitation & flattery & all that). However, it was quickly moved aside in the tool chest for Derek's, which was turned from a lovely bit of finely fiddlebacked Rock oak from another mutual friend.

Yesterday, I discovered a 'fault' with Derek's knife - it won't fit through the kerf left by my ultra-thin dovetail saws! That's ok, Derek - an excuse to make another, using a scrap of the same saw plate the saw came from. Here it is beside it's stable mate. The handle of this one is She-oak. I don't try to copy Derek's exactly - just the general idea.

I've made several of this style of knife over the last couple of years - they make very good gifts, and I've evolved a simple & quick method for making them. Derek epoxies his blades in, which I don't like to do. You will probably never need to change the blade in a normal lifetime, but I'm always keeping an eye on posterity.. So my first knives were assembled with a split boss of brass, slightly tapered so that when pushed into a hole, they tighten up & hold the blade firmly. It looks interesting, but it's a fair bit of mucking about turning the boss & slitting it in halves, & getting it all right, so I tried a much simpler technique, which goes like this:

Assemble the raw material - in this case, a scrap of Mulga (I think!), a bit of a broken stainless-steel kitchen knife, and a ferrule cut from a dag-end of heavy gauge copper pipe the air-con installers chucked at the skip from up on the roof, & missed (I picked it up as I walked into the buiolding next morning. ). Cut your blade so that it is a snug fit in the ferrule as shown.

Before fitting the ferrule, drill a hole in the end with a drill just a tad thicker than the thickness of your blade material, then turn down a spigot for the ferrule. Make it a very tight fit, and before you bang the ferrule on, cut a saw slot right down the middle of the spigot (I forgot to take a pic of thhis !)Use a saw which makes a kerf that is the same thickness as your blade material or a bit less. OK, now drive the ferrule on - it should be a firm fit, but when you fit the knife, it will tighten up more, anyway.

OK - finish knocking off all the bits that don't look like a marking knife, & pretty it up how you like. Now, shape your blade as shown, with a tang that will be a firm fit in teh drilled hole. Grip the blade in a vise, line it up with the slot in the spigot and gently drive it in until the shoulders have seated at the bottom of the spigot. If you calculated it all correctly, it should be rock-solid and need no glue. You can now shape the exposed blade on the grinder, and sharpen it how you desire. I've tried a few fancy shapes, but have decided either straight sides or a slight taper looks & works best for me.

Here's the finished article alongside an old version with the brass boss - a half hour's work vs an hour plus for my old style, and just as solid...

Someone on the forum took Derek to task for these knives, saying they were a bit too dainty for everyday use, but I have found them quite rugged - you can press as hard as you like & cut much deeper than necessary on a single pass on any of the woods I work with. P'raps that person only works with Iron Bark & Lignum vitae..

Cheers,