How to Make a File Knife - Stock Removal

Today we are going to be making a knife from a very common and

cheap tool; a file. 

To begin with, you will need to find a file a sufficient size for the knife you want to make. Usually you can find these at flea markets and garage sales pretty cheap. The other materials you will need for this project are: some pretty hardwood like maple, some 1/4" brass pin stock, a grill, charcoal, heat-proof tubing of some kind, ( for making a forge) a hair drier and some two part epoxy.

 Your tool checklist will include: a belt sander or file, a drill and

1/4" metal cutting drill bit, a small ball peen hammer, tongs or long vice grips, a hacksaw or bandsaw, clamps and a paint can of any kind of oil.

First we are going to make our forge. To begin with, drill a hole the size of your pipe in the bottom of your grill. Now secure the pipe in the hole, with about ½" sticking up in the bottom of the grill. Then duct tape the hair dryer to the other end of the pipe. When the hair dryer is on, it supplies a constant flow of air to your fire on top, and we will use it for the hardening and annealing of our knife. Note: if you are confused, YouTube making a forge, there are a lot of detailed videos there.

Begin by starting up the forge with lump charcoal and turning on the blower. Now heat as much of the file as you can to a dull red. If you need, you can heat one side up, then flip it and do the other side. Once both sides have been or are red, bury the file in sand. Once it cools, it is ANNEALED, meaning it is as soft as it can get. Now, using a bench grinder or file, you can shape your knife. 

Once you have the shape you like, it's on to the next step: putting on the bevel.

To grind the bevel, you need a belt sander with metal abrasive 

belts. If you do not have one of these, a very rough file will work as long as your metal is annealed. Using a file is tedious, but you are not going to mess up easily at all. With a grinder, always have your would-be blade up. First establish a good 20 degree bevel, then by rotating your wrist minutely clockwise you can make the grind line get taller each pass on the grinder. Once you have the grind established, keep thinning it out until the edge is about as thick as the a piece of paper. DO NOT GET IT SHARP. If you do this, the edge will melt off in the hardening process and ruin the blade.

Now you need to drill your holes.  If you are not using a brand new drill bit, it won't cut. (A little tip: use Ace brand drill bits, they are the best for this kind of stuff) And if you didn't anneal your metal, the drill will not cut at all. That said, position your holes where you want them, and drill away. I really advise using a drill press for this, and if you don't have one, try to find a friend that has one and will let you use it. 

Once you have done all of this, it is time for the heat treat. Get your forge fired up, and place your blade in the hottest part of the coals. Make sure the hair dryer is going good, and get the blade part up to a bright orange color. Once the entire cutting edge part is orange, grab it with your pliers and dunk the blade in your oil. But don't just dunk it, move it around in the oil. This helps air pockets from forming on the knife and lessens the chance of warping. This is called hardening. 

(And it MUST be oil; water will not work, for it is too violent of a quench. If you were to quench it in water, it would get tiny little cracks in the blade that would grow in size with use of the knife and ruin the blade)

 Take it out and run a file loosely across the edge. If it slides over with no catching, it is hardened. If the file bites into the metal, it did not harden properly and you need to try again. After this, take your knife and check it for warping. If it warped, DO NOT HAMMER ON IT. The knife is very brittle and would break. Heat the knife up to a red and then bang on it and re-harden it. 

If your knife was straight, put it in the oven set for 400 degrees and leave it there two hours. When you're ready, take it out with pliers and dunk it in some water. This process is called tempering; it takes some of the hardness out of the knife and ensures a good edge. Now take your knife back to the sander or file and take all of the scale off of the bevels. Now you can get it as sharp on the grinder as you want.

OK, on to the handle. First, trace the handle of your knife onto a piece of your hard wood, twice. Using a bandsaw or hacksaw, cutting outside of the line, cut the pattern you traced out. Now position one of these slabs underneath the actual handle, get it how you want it, and drill holes that line up exactly with the ones in your file. Do the same with the other side. 

Now cut two 1 ½" lengths of your pin stock and put them into the holes. Once done, you can do the pre-final sanding and profiling of the handle with the pins holding the wood in place where it will be when it's all said and done. Once you have the shape of the wood slabs lined up with the tang of the knife, take the pins out and cut them down until, when they are slid into the holes, there is only 1/8" protruding on each side. 

Now take all of the parts and set them out. The handle slabs should be inside-up and the pins should be easily accessed. Now mix your epoxy, and smear a thin layer in both sides of the tang and the insides of the handle slabs. Line all the holes up, and insert the pins. Now take the back of your ball-peen hammer and peen the pins over gently on each side until they are good and flat. Clamp it up good, but not so tight that you squeeze all the epoxy out.

Once the epoxy cures, you can do the final shaping on your sander... or with sandpaper. When you have a shape you like, rub the handle down with a few coats of oil, and ... viola, you have a file knife.