Introduction: Creating a Bush Knife From an Old Hand File

By Tom
About: I'm the kind of person who's mind doesn't stop. Literally, I take medication to fix that just so I can sleep at night. I have an unhealthy obsession with making things and believe, firmly, in sharing what I le…

I love making my own tools. From chisels to crooked knives, the process, I feel, binds that tool to you and personalizes it in a way that gives it value that a store bought item can't. On this one, I had an old hand file from the early 1900's that I was saving for just such a project.

After discussing with my wife how I was going to do the build, I figured it would be interesting to turn the design of the project over to her, with the agreement that I would build it exactly how she envisioned it. So I handed her the file and some card stock to draw it out on and she went to work. One of the stipulations she had was that was that she liked the design the files ridges had on the blade. Unfortunately, I knew that I'd have to reduce it's thickness and the ridges would have to go, but decided I could give it the texture, which I'll show later on.

In the main pic, I show a case, which I'll likely make an instructable for later on, but for now it's just the knife. This is a generic case I design to fit a variety of knives. Only the bottom 3" are sewn, and the body is held shut with the belt so that it can be adjusted to fit a variety of blades.

Step 1: Tools and Material

Tools;

Vertical Belt Sander with 60, 120, 220, 300 grit belts - for grinding and shaping
Angle Grinder w/ cutoff wheel, sanding wheel, and grinding wheel - for the rough work
Titanium drill bits - For drilling through handle for pins. If all you can get is TiNite, don't worry, I show how to anneal the handle later
Torch or fire pit with shop Vac - cheap way to anneal the handle.
Vernier Calipers - verifying the consistency of the thickness
Clamps - for clamping the handle
Spray Bottle - cooling the metal as you work

Material;

File -  Newer files are case hardened so older files are definitely better
Sand paper - 60, 100, 150, 220,300, 400 and 600 grit for progressive sanding.
Wood - To make your handle out of. I used purpleheart, but the choice is up to you
Brass pins or Brass Rod - securing the handle to the knife
Epoxy Cement - again, securing the handle
Tape - I can never stress how important taping the blade is when you're working the handle. One slip and...



Step 2: Choosing and Testing Your File

For starters, you should avoid most newer files. They are, what's called, case hardened, which means only the outer surface is actually tempered with a high carbon content. Inside, many of them are mild steel. The file I used was found at a flea market where I paid .50 cents for it, along with a box of other "junk" tools.

There are a couple of ways you can test your file;

Strike Test - Like using an old flint and steel, just find a flat surface on the file and glide it against the sharp edge of a piece of flint, (or any sharp igneous rock should do). I've found that most case hardened steel doesn't have the carbon content to make a spark this way so it's a good benchmark for you. You can grind down into the file a bit and test it this way to guarantee it's hardened all the way through.

Spark Test - Grind a bit of metal off the surface, then do a spark test on the file. It's a lot less complicated than you think. High carbon steel makes LOTS and LOTS of sparks with few lines. Milder steel will often shoot out first before exploding into a spark.

Step 3: Prepping Your Bar of Steel

Most of the rough out work can be performed using an angle grinder with the grinding disk. After removing the grooves, I was left with a piece of metal that was .200" which was a bit thick for what I wanted. I worked the material down until the metal was .165" on the vernier caliper. The battery was almost dead on my caliper, and the display was blinking, so unfortunately, I didn't realize it showed as blank until I uploaded the pic much later on, but trust me, I worked it with the grinder until I had a uniform thickness along the length of the bar. I finished it by smoothing with the sanding disk to smooth it better.

***It's very important to cool your bar often as you grind it as you don't want it to get too hot. I've had projects that have lost their temper due to heating from prolonged grinding and have found that regular spraying prevents that. During the thinning process I went through 2 bottles of water for cooling.

Once you have your blank piece of bar stock, you can transfer your design and get ready for shaping.

Step 4: Roughing It Out

Once your design has been transferred to the bar, you can start roughing out the basic shape. It's a bit easier to do some of the course work with your angle grinder, then fine tune with the belt sander. I'd suggest you leave a millimeter or two of extra material on the handle since you'll likely be sanding it off once the wood is in place.

Roughing out the bevel for the edge can be a bit trickier, especially if you don't have the proper knife making equipment. What I did was create a jig by clamping a piece of wood to the table of my belt sander to create the angle that I wanted. The hardest part rotating it to create the tip. I started off by course grinding with 60 grit, then as I got to 90 percent completion, I started switching the belt to finer and finer grits until reaching 600 (wet)  to create a smooth finish.

A Few Choices In Creative Style;

Contrary to what many people think, a knife doesn't have to be perfect and shiny. If you prefer the traditional mirror finish you can keep sanding with progressively finer grits, ending off by wet sanding with 2000 grit paper. However, I prefer a decent patina on a blade which can help protect high carbon steel from rusting when it gets wet. One way to do this is by applying heat (which I'll show in the next step as I talk about annealing the handle for drilling).

Now, as I mentioned in the beginning, one of the stipulations my wife requested was that I leave the file grooves intact. Since I needed to reduce the bar, I couldn't do that so after I'd created a nice smooth finish on the knife, I put a fresh 40 grit belt on the sander and resurfaced the entire piece, making sure I kept my lines running all in the same direction. It turned out pretty good, but still didn't have the contrast that a patina would give it. Next to heating.

Step 5: Annealing the Handle for Drilling

To make the handle soft enough, you need to heat it to red and keep it there for a few minutes, then finally let it air cool until it reaches room temperature.

***It's very important that you do not heat up the blade, only the handle. I've tried a few different methods of keeping the blade cool, including enclosing it in clay before heating, but found that simply being careful not to get to close to the blade worked the best. I usually only heat up to where I intend on mounting my pins so as not to kill the temper on the blade itself.

Not having an oxy-acetylene torch on hand to make the process easier, I opted for a simpler setup. One way of doing it is to use two propane torches, hitting the handle from both sides at the same time, then slowly moving up the handle until you reach a couple of inches away from the blade. This method is long and tiring so I used a much easier method. I built a camp fire, waited till it had a decent coal base, sunk the handle into the coals, then turned my shop vac on reverse to blow air across the coals, making the fire even hotter. It worked perfectly and a quick flint test after ensured that I hadn't messed with the temper on the blade itself.

Step 6: Drilling and Pin Choice

Having annealed the handle made it easy to drill through the hand with my TiNite bit. You just have to make sure you use lots of oil as you're drilling. I decided to use some 1/8" brass rod instead of the standard knife handle pins that you see in the second pic. I like the understated look of the brass rod, plus it allows you to make a rounder handle. If you do prefer the pins, I purchased these at Lee Valley Tools, which I'm pretty sure operate across North America so they should be available to both Canadians and Americans.

Step 7: Final Sanding Before the Handle Installation

To keep the lined pattern I wet sanded with 400, 600 then 1000 grit paper. As you can see the patina stayed in the valley's and the plateau's have a nice polish. This was the final stage for me, as far as the blade itself was concerned. I still hadn't fully sharpened it yet, but it did have a decent edge already from grinding the bevel.

Step 8: Pinning and Gluing the Handle

I find that finishing one edge of your handle scales, where they meet the blade really goes a long way to not accidentally scratching your work. Round them into their rough final shape then give them a light sanding with 150 grit paper. It's also a great idea to put tape over the spots where you intend to drill the scales to prevent the bit from tearing as it pushes through. This is especially important when using very hard woods like ebony and purpleheart.

Next, skim a layer of glue on the scales and put some in the holes where the pins will push through. Don't worry too much if the glue squeezes out a bit because you will be sanding the whole thing down after, just try not to get any on the blade. It's a good idea to wrap the blade in tape to ensure it stays clean.

When all the parts are ready, sandwich it all together, push the pins through so that they are sticking through both sides, then clamp the scales to the blade. Let them sit for a couple of hours until the glue dries.

Step 9: Sanding and Shaping the Handle

It's time to return to the belt sander to remove all of the extra wood for the handle, and to give it the final shape. It's helpful to stop every now and again and take look down the blade to make sure that the handle thickness on both scales is the same. It's also useful to use your vernier calipers if you have them.

Again, you want to sand with 60, 100, 150, 220, then 300 grit sandpaper. You can wet sand with 400 if you really want to but it's not necessary. If you decide to use purpleheart like I did, it's important to let the knife sit for about an hour before finishing. Purpleheart tends to turn brown when freshly sanded, then as it is exposed to air will turn purple.

Step 10: Finishing Up

The last step is finishing the wood for your handle. On occasion I'll use an epoxy coating, (5 min. epoxy smoothed on by hand) but more often than not I use a beeswax polish. I like to apply 3 coats, waiting an hour between each, then finally coating the entire knife to protect the finish of the steel.

That's it. Now it's time to sharpen your new blade. Tool making can be a fun project, and if you decide to take it on, I hope you have as much fun as I did.