A New Striking Knife

striking knifeAfter several years of hard use, my trusty striking knife broke on me over the weekend. This was one of the first tools I ever made for myself so there was a moment of sadness, but only for a moment as I’ve been looking for an excuse to make a new striking knife (like we ever need an excuse for a new tool).

The design of my old knife, while functional for several years, was bound to fail eventually. Without some type of ferrule to reinforce the area where the blade is inserted into the handle, the side grain is left unsupported and prone to breaking out when too much force is applied down on the knife, which is exactly what happened here. One solution is to make the blade run all the way through the handle or simply rivet scales to the blade, however, I was working with a broken jigsaw blade to make my striking knife blade so this was not an option for me at the time. No matter, I was never really crazy about this knife to begin with. It worked ok, but something about the spear point design just didn’t do it for me. I can’t explain it really but it just didn’t feel right. It was also more difficult to sharpen being a spear point and in use, I only ever used it as a right handed single edged knife anyway. I can’t recall ever using the opposite side of the spear point. So for my new knife, I decided to change the design.

striking knifeTo start with, I decided to use a longer blade stock to provide more support. I had two old worn out small files, a flat and a rat tail, that would make excellent knife and awl blanks, almost like they were meant for the task. Therefore, I decided on a double ended striking knife with an awl on one end and a knife on the other. The tangs of the files were round, unlike most files which have square tapered tangs. This made mounting the tangs in a new handle easy as I could just drill a hole, however, it also means that they might spin loose in the future. Time will tell. The old file handles also had ferrules that I could reuse on the new handle.

The first step was to separate the files from their existing handles and remove the ferrules from the handles carefully so I could reuse them later. Once this was done, I annealed the files by heating them to cherry red with two propane torches and then letting them cool slowly in a pile of ashes in the fireplace. This made the metal soft enough to work with hacksaw and files.

striking knifeI started by working on the awl end. Unlike my woodworking, I use power when doing metal working. I don’t like metal working. However, being resourceful (read cheap) means that sometimes I need to work metal when I need a new tool. At any rate, I have a few power tools I mainly use for home improvement but they double as hack metal working tools as well.

I chucked up the round end of the softened rat tail file in a drill press and worked the blank with a bastard mil file while it was spinning. This is my make shift metal lathe. The file work was slow going but eventually I was able to shape the awl. The final sharpening of the awl point was done with various grits of sandpaper wrapped around a flat wood block. I didn’t want to gouge my oil stones for this rough work. At this point, the awl end was done. I decided not to heat treat the awl end so it would be less brittle and less likely to snap in use. It also makes it easy to reshape and hone the point with simple files and honing stones or sandpaper.

striking knifeWith the awl end completed, I turned my attention to the knife blank. I chucked up a small belt sander upside down in a machinist vise (remove the dust collection bag first to prevent a fire). Using the belt sander with a coarse belt, I sanded the teeth off of all four edges of the small flat file. Once the teeth were gone, I used a hacksaw to cut the flat file to the length I wanted and then used the grinder to grind the chosen skew angle and rough bevel. The knife is a single skew, single bevel type set up for right handed use.

After lapping out the faces of the knife, I heat treated it using two propane torches. I heated the blank to cherry red and quenched it to quickly cool and harden the steel. However, this made the steel so hard that a hardened file just skittered across it so it needed to be tempered to be able to be sharpened and to prevent it from snapping in use. I lapped the faces shiny so I could see the color change in the metal as I tempered it. Using a single torch I slowly heated the knife blank, watching the color change where I had just polished the metal. When the color got to a dark straw color, I quickly quenched the knife again to prevent over heating. Once you get to a dark straw color, it goes to blue quickly thereafter so you have to watch closely and work quickly. If it gets to blue, the metal is too soft to hold an edge. If this happens, you will need to reharden the blade, then try the tempering process again.

striking knifeI chose a piece of bubinga I had in the offcut pile to use as a handle. I planed the blank square and cut off a 3½” section. I used the drill press to drill a hole completely through the blank for the tangs of each end. The ends were then shaped for the ferrules using an old plug cutter in the drill press. This worked very well. I got lucky to have a proper sized plug cutter still left in a box in the back of my garage (from my power tool days). The ferrules were heated to expand them slightly and then fit to the ends of the handle. The handle was then shaped with a spokeshave, rasps, files and some sanding. The knife and awl were inserted into the ends of the handle with some epoxy to hold them and keep them from spinning. Finally, the whole thing was finished with linseed oil.

So far I like it, though it hasn’t really seen a lot of use yet. The handle might be a little full and may need to have it’s shape refined a little more, but I’ll use it for awhile before I make any changes. With the tangs of the two ends going all the way to the center of the handle and the ferrules supporting the ends, this striking knife should be around for a long time.

Now to get back to working wood!


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