Tuesday, June 20

Make Your Own Bushcraft Knife

DIY Bushcraft Knife - How to Make Your Own

Making a Bushcraft Knife Out of an Old Saw Blade

In this tutorial, we will go through the steps you can take to repurpose an old saw blade into a functional, fully hardened and tempered knife complete with a paracord-wrapped handle.

The knife in the above photo was created using these tools and supplies:

  • Old single-buck crosscut saw blade
  • Hacksaw
  • Parachute cord
  • Sharpie (for tracing the outline of your knife)
  • Heat source (I used a propane-powered forge, but an oxy-acetylene torch will do the job, too.)
  • Tongs (to hold the hot metal while you heat it)
  • Bench grinder and/or mill bastard file
Step One: Finding Usable Steel

You can find tool-grade steel online for reasonable prices, but for this tutorial I want to focus on the least expensive way to create your bushcraft knife. That means using what's on-hand (circular saw blades, handsaw blades, rebar, etc.) or what you can find at a flea market or yard sale.

This is a (relatively) old crosscut saw I picked up a couple of years back. It's a little thin, but the steel is solid. I was confident that it would make a decent, lightweight blade that I could pack with me on hiking trips.

As you can see in the photo, I started cutting out my knife blank by clamping it in a vise and using a hacksaw. This was after I heated the blade up and let it cool down slowly to soften it.

Step Two: Soften the Steel Before You Cut

Unless you have an angle grinder (a DeWalt will run you between $50-$80 brand new), you will need to soften the steel before you start sawing on it. Otherwise, you'll wear out the blade of your cutting tool (and your arm) pretty quickly.

I have the advantage of a double-burner gas forge to use for this purpose, but you can accomplish the same thing with:

  • An acetylene torch.
  • A wood fire.
  • A coal fire. 
Regardless of your heat source, you want to get the steel up above cherry red before setting it down on a concrete block or bricks to cool down slowly. This is a simple way to anneal the steel or soften it. 

In this photo, I'm heating the old saw blade up in sections since it's too long to fit inside the forge. 

Step Three: Rough Cutting the Steel

For my first few knives using this process I just used a hacksaw. It took some time and some sweat, but it was a lot less expensive than using a cutting torch.

The knife pattern I used is available for free from D. Comeau Custom Knives. He has a wide selection of knife patterns that you can download as PDFs and print off for your personal use.  

Once I got the rough cut done, I took the piece of steel with my traced knife pattern over the bench grinder and spent a while grinding out the profile of the blade. 

Now that I had the profile the way I wanted, I was ready to harden the blade. So back to the forge (or your heat source) we go.

Step Four: Hardening Your Blade

Using your heat source, you want to bring the color of your blade above cherry red. By quenching the steel at this point, we're rapidly cooling it and arresting the internal structure of it. 

This quenching makes it hard, but also brittle. If you were to clamp the blade in a vise after hardening and pull on it, it would snap in two. This is because the internal composition has changed from being interlocked and tightly packed to being just tightly packed liked grains of sand stacked on top of each other. 

A note on quenching: If you use water to quench your blade, it will cool too quickly. A better bet, and what we use in the shop, is vegetable oil. It cools more slowly and doesn't give off toxic fumes like used motor oil or similar petroleum products. It's also very cheap!

Step Five: Tempering Your Bushcraft Blade

After your blade has cooled down completely on your concrete block or bricks, it's time to polish it up. The reason we polish the blade is to see the tempering colors as we slowly heat the blade. 

If you can see "silver" on your knife blade, you're in good shape to start the tempering process. 

For this we use a propane torch to do a draw temper along the spine of the blade (the side opposite the blade edge). We gradually heat it up and watch as the silver becomes a "light wheat" color. This is usually enough of a temper to allow for sharpening. 

In the two photos above, you can see almost all of the tempering colors. For this knife, I ended up going to the top of the tempering scale in temperature and color. The bottom photo shows the "light blue" color that you get if you continue to apply heat to the steel after you see the "light wheat" and "purple" come through. 

With a blade this thin it's tricky to temper it evenly with just a torch. It's great to have a few blanks handy that you can practice tempering on until you develop some skill at it. 

After the blade is tempered, we can move on to Sharpening and Handling.

Step Six: Sharpening Your DIY Bushcraft Knife

Now that the blade is tempered, we've taken some of that hardness and brittleness back out of it. This makes it so we can sharpen the blade and it has more flexibility. It's less likely to snap when put under pressure. 

My preference is to hand-sharpen my blades. It generates less heat (this can affect the temper you just did) and you have more control. It does take some practice to develop good sharpening habits. 

Here's a quick refresher on sharpening with a metal file:

  1. Never saw back and forth with the file. Always move in one direction - away from you and across the blade edge.
  2. Don't over-sharpen. If you can feel a burr on one side of the blade, you've gone too far. To fix it, take the file flat over the blade. This will dull it very slightly and take off the burr. 
  3. Don't use a rasp. Pay close attention to how rough the file is that you're using. It should grab the metal as it slides across, but not tear it up. 
Step Seven: Putting a Handle On Your Knife

For this knife project, I chose to wrap the handle with olive green parachute cord. It makes the grip a little softer and you also have some cordage on-hand should you need it in the backcountry. 

When you're using p-cord for handling, I recommend gutting it first. Pull out all of the internal strings so the cord will wrap tightly around the handle. 

After you gut the cord, seal off the ends with a lighter by heating them up and pressing the fibers together. This will prevent fraying. 

Starting at the blade end of your handle, lay the p-cord perpendicular to the handle and then start wrapping the cord around it. 

Tuck the other end under the last few wraps you do to secure it. I then take a lighter to the whole thing to slightly melt and bind it together. 

That's it in a nutshell!

Sometimes it's easier to see the steps in action. If you're interested in a more in-depth video tutorial version of this process, send us an email at diyblacksmith@gmail.com.  

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