John Burrill 5/2/2011
I'm a fairly new knife maker, and have been making a few slip folders; a dozen so far. A constant challenge is to get a nice nail nick. I've tried a 4" aluminum oxide tool post grinding wheel dressed off to a 45 degree angle, and also both 3/4 inch and 1 1/2 inch dovetail milling cutters. I'm not getting a clean nick with the grinding wheel because the sharp edge breaks down, and the dovetail cutters'sharp corners don't stand up to the job, even though I am using annealed steel (O-1 and CPM 154)just as I buy it. I use a milling machine with about 400 rpm shaft speed speed on the tool . Maybe I need to find better quaity wheels or cutters? I really like the nail nicks that are straight across on the top and curved on the bottom side such as you get with these shapes, and am anxious to solve the problem. Does anyone have any ideas to share on how to achieve this? By the way, this forum is fantastic resource for a new knife maker.
Hi John,
I use a fly cutter for making nail nicks. I built the tool holder years ago for another project, then started using it for cutting nail nicks. The tool bit is a standard, 1/4" bit with a soldered carbide insert. I ground the carbide insert to about a 45 degree angle on the bottom. The tool bit is adjusted in the holder to make about a 1 1/2" radius (3" diameter) swing.
I cut nail nicks before I grind the blade bevels. I usually cut the nicks half of the thickness of the blade steel. This leaves the nail nick at proper size once the blade bevels are ground. You need to have the blade blank firmly clamped to a solid surface when cutting. This keeps the blade from bouncing from the impact of the tool; which will break the carbide insert tip. I'm not sure what speed the I run the milling machine at; but it's fairly slow.
Another simple method of making nail nicks is to use a chisel. Grind a chisel to the shape that you want the nail nicks to be and either use a hammer or a hydraulic press to make the nick. The only problem with this method is that it tends to bend the blade a little, so you'll have to bend or grind the blade flat after making the nick.
Steve:
Thanks very much. Both of these methods sound great, and had not occurred to me. The fly cutter idea in particular is one I can do. I will experiment with the chisel technique as well. If it works well, it would involve less set up time.
John
