Introduction: How to Make a Knife From an Old Saw Blade
With a few simple tools and a couple hours of work, you can turn an old, worn out saw blade into a fully functional knife. Saw blades are a good source of carbon steel, and allow you to create a knife for almost no money at all. I got the idea for this project after seeing danthemakerman's instructable called "Saw Blade Knife". If you buy a bar of carbon steel for knifemaking, it will cost about $25. Since this knife is made of an old saw blade that would be thrown away otherwise, the steel is absolutely free. I made this usable knife with common tools and an old saw blade in just a couple of hours.
Step 1: Tools and Materials
For this project, you will need a few readily available tools and materials. I used tools that I had on hand, but the knife can be made with different tools that do the same job.
- Safety equipment (Glasses, earmuffs, gloves)
- Angle grinder
- Drill and drill bit
- Torch (I used a backpacking stove, but it needs to be able to heat the metal to red hot)
- Saw Blade
- Paper towels
- Quenching oil
- Handle Material
- Sharpening system (I used a whetstone)
Step 2: Make a Template
Some knifemakers make a template out of plywood so that they can see what the knife will feel like before making it out of steel. I just drew a template on paper and cut it out with scissors.
Step 3: Cut the Blank
This step is when the knife really begins to take shape. First, you will need to trace the template onto the saw blade. Then, use an angle grinder, metal cutting bandsaw, or hacksaw to cut out the shape of the template. I just used an angle grinder with a cutoff wheel.
Step 4: Grind and File the Blank
After you cut the blank, you will need to use an angle grinder, belt grinder, or files to bring the knife down to it's final shape. I used a combination of an angle grinder and files to do this. Also, you will need to take off any paint that could affect the heat treat.
Step 5: Mark and Grind the Bevels
The bevels are what takes the blade down from the full thickness of the metal down to an edge that can be sharpened. To start, mark where the bevels will be. I marked the bevels to be about 2/3 of the blade. If the bevels aren't big enough, the blade will have too steep of a cutting angle and won't cut well. To prevent this, the bevels should go up at least half of the blade. There are many ways that the bevels can be made. I used an angle grinder and tried to keep at at as constant of an angle as possible. However, it is very easy to grind away too much metal this way. You can also use a belt grinder or a filing jig like seen HERE.
Step 6: Heat Treat
Heat treating is what makes the steel of the blade hard. If the steel is not hardened, the blade won't stay sharp for very long. To heat treat the knife, you first have to heat up the metal until it is red hot and non-magnetic. When a magnet doesn't stick to the blade, it is at the right temperature. To do this, I used a backpacking stove. You can also use a torch or a forge, but I didn't have either one of these. After the metal is red hot, put the blade into oil. This will rapidly cool the blade, causing it to harden. Once you quench the blade in oil, the blade is very hard, but brittle. To slightly soften the blade to make it less brittle, put it in the oven at 350 degrees for two hours, then let it cool down on its own. This completes the heat treatment process.
Step 7: Clean-Up
After the blade is heat treated, there will be a layer of black oxide on the outside of the blade. To take this off and make the blade shiny and smooth, use sandpaper to grind the oxide away.
Step 8: Handle
After the knife is cleaned up and smooth, a handle will be needed to put on. I just used paracord to make a cord wrap, but you can also use wood with glue and pins to hold it on. To make the handle wrap, I first drilled a hole in the end of the knife. I then passed the core through and tied a knot to hold it on. Then, I wrapped the handle, twisted the end around, and secured it by melting the end of the cord.
Step 9: Sharpening and Finish
So, the knife has been made. The last thing to do is to sharpen the blade to make it functional. I used a whetstone for this. You can also use a sharpening system or other means of sharpening the knife. After the blade has been sharpened, it is finished.
As you can see, with a little work and some simple tools, you can make a knife out of an old saw blade for almost free.