For a while I’ve wanted to make a knife. I finally decided to give it a try this week. Making a knife requires using good steel that will harden and take an edge. Normal steel like you see at the hardware is low carbon steel and can’t be used to make a knife. I had read that old metal files were a source of high carbon steel that people can use to make knives. Metal files are very hard and must first be softened so they can be worked. To be softened, they must go through a process called annealing. This requires the files be heated up until glowing orange and then allowed to cool slowly.
To anneal my files, I used my charcoal grill. I built up a fire and then used a blower to really get the fire going. I placed four old dull files into the coals, allowed them to get a uniform glow, and the plunged them into a bucket of sand to cool. Normally, temperatures are controlled precisely when heating steel but my crude methods do not allow for this and I have to go by color of the glowing metal. Once the files had cooled I removed them from the sand. Two were straight, one had a slight bend, and the final one had a large bend. To test the hardness of my annealed files, I filed them with a normal metal file. The file removed material easily from my annealed files indicating that I’d successfully softened them. I used my 4.5″ hand held grinder to remove all of the teeth from the two straight files to create a blank to begin working with. Shown below is one of the cleaned up files and the badly bent file.
I wanted to create a simple bushcraft knife and sketched an appropriate shape out on my blank. Next, I used my hack saw to remove the bulk of the waste material. From there, I used my grinders and belt sander to further refine the shape. Finally, I needed some holes in the tang of the knife for the rivets to pass through. The shaping went easily but the drilling gave me some trouble. One of the holes drilled easily but the other two had problems halfway through. I believe that the metal in these spots didn’t get properly annealed and was still hard. I tested other spots on the tang with a file and found them to be soft. Apparently, I’d chosen to drill in some of the hard spots. I eventually got the holes drilled and was left with the shape seen below. It looks like a knife but the steel is still soft which means it won’t take and hold an edge.
To harden the knife, I went back to my BBQ grill. I built up a good fire and used it to warm a scrap piece of steel. Once this piece of steel was warmed up I dunked it into my can of quenching oil to warm the oil up to around the recommended 120 deg F. Though you might not expect it, to a point, heated oil cools the blade faster when quenching than cool oil. I’m using canola oil because it was cheap, easily available, and it said to work well. From what research I did, old Nicholson files are probably made of W1 steel. The W in the type of steel stands for water which is the recommended quenchant for this type of steel. I chose to use oil because I’m not totally sure what type steel I have and using water, which cools faster than oil, can cause cracking and warping when used on the wrong type of steel. On the other hand, if the oil didn’t work, the knife wouldn’t harden and I could try again using water.
Once the oil was up to temp, I plunged the knife into the coals doing my best to make sure the blade was equally heated on both sides. Hardening steel requires the temperature of the steel be increased above it’s critical point temperature and then quickly cooled. In the backyard, with high carbon steel, you can determine the steel has reached this point by observing the color of the metal and also by testing it with a magnet. Once the steel has passed the critical point it is no longer magnetic. I heated my blade until It achieved a uniform cherry red color on the blade. I then checked it with my magnet which wasn’t attracted to the blade.
Satisfied I’d exceeded the critical point I rapidly removed the blade from the coals and plunged it straight down into the oil. I moved it back and forth in the oil while waiting for the blade to cool. I’ve read that you shouldn’t move the blade side to side or up and down in the oil while it is cooling because the blade may warp. After a short while the blade stopped shaking indicating it had cooled enough but I left it in the oil a little longer. Note that a small fire may pop up while quenching. Mine went out fairly quickly and wasn’t a concern for me as I was wearing heavy gloves and had the lid of the paint can near by if needed to smother the fire.
Once the blade had cooled I removed it from the oil and tested the hardness with a good metal file. The file should skate off the surface of properly hardened steel. I’m not 100% sure exactly what “skate” means in this case but when I tried it the file didn’t bite in. It only left a slight scuff that was very different from what happened when I filed it before heat treating. I took this to mean that the steel had hardened properly. At this point the steel is very hard but also brittle to the point that if dropped it could break.
To be a useful knife, the steel must be softened a bit through a process called tempering by heating again. Before heating, the black scale should be removed from the blade. This is done so that the color of the blade can be seen after it has been tempered. As before, the color can be used to provide information on the temperature of the blade. This time though the color remains after the blade has cooled allowing you to know the temperature the blade reached.
I used my kitchen oven to temper my knife so the color of the blade isn’t as important as it would be if I’d used a torch. I set the oven for 400 deg F and left the blade in for an hour. Once I removed it, I observed that the blade had a yellowish straw color which is what I was aiming for. You can see the blade has been colored in the picture below, but it was lighter in person and covered the rest of the blade. I’m surprised it showed up as well as it did in the photo.
Once the blade had cooled again I started working on the the edge of the blade. I freehand sharpened the knife and easily reached the point where the blade would slice paper. I though the edge was a little thick though and worked to reduce the angle with my belt sander. I turned to my Lansky sharpening kit to put a small secondary bevel on the blade and put the final edge on it. This took longer than it should if I ‘d properly ground the bevel when it was in the annealed state. A lesson for next time.
Happy with the edge, I wrapped the cutting portion of the knife in tape to protect myself and started work on the handle scales. I used some Walnut I had sitting around and rough shaped the scales with the belt sander. In the picture below, I’m using the brass I plan to make the rivets out of to hold the scales together to match the ends.
I clamped the scales together on the knife handle and used my arbor press to drive the brass rivets into place. I should have used some epoxy here to secure the scales on but it slipped my mind. If the scaled end up coming off I can epoxy them on then.
Next, I cut them down, sanded the rivets flat, but not flush, and peened them over with a punch. From here it was back to the belt sander to finish rough sanding the wooden scales.
After rough sanding, I hand sanded the Walnut down to 220 and applied some boiled linseed oil. Here’s a pic of the finished knife. There’s still some scuffs on the primary bevel and the side of the blade isn’t flawless either. I’m ok with this because this my first knife and I’m more concerned about seeing how it hold up than making it pretty. I wasn’t aiming for any specific dimensions but the spine is 0.15″ thick and the knife is about 8.5″ long.
The little cutouts on the top are called jimping and provides a place to rest your thumb if you’re holding the knife in a specific way.
I gave the blade a test run cutting some rope and turning up some curls on a piece of oak. The knife accomplished these simple tasks with no noticeable affects on the edge.
No post on a knife is complete without a picture of the knife stuck into a block of wood it seems. So here is mine.
If you’re interested in making a knife head over to BladeForums or search online for more information. There’s a lot of good information on Youtube and Vimeo. One specific series of videos by someone named GreenPete has produced four videos on making a knife using primitive methods which are very good.