Making a Knife Blade

Ingvar Gråhök explains how he made his own knife blades

I decided to see how hard it would be to make a knife. Doing this in a 100% medieval style is not easy to do in the home, since finding raw materials in period qualities is hard. But, in this day and age, you can find good materials by a little bit of searching. I decided that O1 tool steel would be my material of choice, based on the fact that it is an oil-hardening steel, frequently recommended for knife-making. I started with the purchase of a 3mm x 30 mm x 500 mm flat-stock bar from RS Components (they’ll either do mail delivery or let you pick it up at the least inconvenient store of theirs).

I also decided to manufacture my knife using only “material removal” (essentially grind, cut and file the blade to shape, rather than using heat, hammer and an anvil to do the rough shaping, followed by filing and grinding to take it from rough to final dimensions). Material removal is more wasteful in terms of material, since you end up removing a fair bit of the precious steel, something that can be lessened (if not totally avoided) by smithing it into shape.

Once you have the steel, you need to decide on “how long a blade” and “what sort of tang”. Knife tangs come in two main variants, the “full tang” (a tang that has two handle scales to form the grip) or a “rat-tail tang” (thin tang that the handle is slid on to; either through the whole handle, or partially into the handle).

After that, you probably want to lay out the blade (and tang) on the steel. For this, pretty much anything works, I used a Sharpie with a relatively fine point, to mark out the cut-off line, marking the blade shape and the tang.

Once your layout is done, you can cut. A metal hacksaw, or a jeweller’s saw would work fine, but I had a Dremel and a cut-off wheel so I used that (you definitely want eye protection, and you may want to use a breathing mask, the dust released isn’t exactly good for you).

To shape the point, you can either just grind it to shape, or cut well outside your line, then grind the last bit to shape. I would recommend the latter, since it’s a lot quicker. For grinding, you can use metal files, hand-sand it, or use a belt grinder (ideally a fairly large sander, but the small hand-held belt sander I have does a passable job).

Once you’ve created the full blade profile, you want to mark out the edge bevels. I simply hold a Sharpie so that I get an approximately consistent distance from the edge to the inside of the bevel and draw that on both sides of the blade. You may also want to mark the centre line of the edge-to-be. The easiest thing here is to use a pen (or layout fluid) to mark the side of the blade, then use a drill bit (metal or all-purpose) of the same diameter as the thickness of the blade.

Now you can grind the bevel, again fully manually or by using machine tools. You want to get it as close to “done” as possible. You may also want to break the edges of the back of the blade. “Breaking the edge” is basically giving the sharp right-angled corner a slight sanding, so that it is no longer sharp and you’re not at risk of hurting yourself (yes, this can be done earlier).

You may also want to clean up the tang. If you went for a full-tang blade, you need to have the tang fully shaped before you go to “hardening and tempering”. If you have a rat-tail tang, you may want to ensure that it’s not full of burrs, as this will make it hard to install it.

Once you’re happy that you’re pretty much at final shape, you can proceed to harden the blade. For this, you need to heat the steel to “critical temperature” (724 degrees Celsius). The absolute easiest way of making sure that the blade is hot enough is to check if it’s still magnetic. If it’s magnetic, you need more heat. If it’s not, your steel barbecue is done. I used a blowtorch for this. Simply place the blowtorch on a stable surface and keep moving the blade (slowly) through the flame. You will probably have to experiment a bit to find the hottest part of the flame, but it will probably be 25-45 mm from the nozzle of the torch.

Now that your steel is nice and hot, you need to quench it. A good choice is vegetable oil, it’s slightly less severe than water, so your blade won’t be as hard. But it’s also less of a risk that you would end up with stress cracks that would ruin the blade. Test that you’ve achieved full hardness by using a file on the blade, if the file “skates” over the surface, rather than biting in, you’ve just hardened a blade.

Unfortunately, you’re not done with heat-treating yet. You also need to temper the blade. The easiest way of doing this at home is to get your oven set to roughly 200 degrees Celsius, then place the blade on a rack approximately in the middle of the oven and leave it in there for 15-30 minutes. This removes some of the hardness, but makes the blade much more ductile, so it doesn’t snap.

Then you can proceed to finishing off the polish and putting a handle on the blade. For a rat-tail tang, you do this by drilling multiple holes, the width of the tang, into wood (or antler, or bone) and glue it into place. If you’ve gone for a full tang, you can rivet and/or glue the scales into place.

After this, “all” that is left is a final sharpening and making a sheath.