Making the HOOKED BLADE
Making knives goes from difficult to easy, metal to wood. But don’t take that to mean the process is time-consuming or fraught with peril. Only that working with metal requires a different set of steps that you don’t use when making something from wood.
START WITH GOOD STEEL. My initial thought of making the knife blade conjured images of hammers, tongs, and fire. Chris’ version starts with a blank of
O1 tool steel from Mcmastercarr (our secret supply source). Using 1⁄2"-wide, 1⁄16"-thick bar stock minimizes the amount of cutting and shaping that you need to do.
PICK A PATTERN. The drawings above show three different sweeps for the blades. You can easily get all three from the stock listed. However, make only what blade you want. In any case, the process for shaping is the same. Start by cutting the blade blank to length. The drawings in the box below take over from here.
Use a punch to mark the two rivet holes that secure the blade to the handle. You also need to form an ever so slight chamfer on the holes, as shown in Figure 1 below. This allows the copper rivets to grip the blade when they’re peened.
The steel blank comes annealed but it’s still a good idea to drill with a slow speed and to use cutting fluid for a smooth hole and to carry away chips.
The basic shape of the blade can now be cut with a hacksaw, as shown in Figure 2. Follow as close as possible to the pattern you mark on the blank.
Refining the shape and working down the layout lines comes next and depends on your equipment. You can get it done quicker with a grinder or disc sander. Keep a cup of water nearby to cool the blade as necessary.
However a couple of files work just fine, too. Getting a smooth, even profile is much easier now than when the blade has been hardened later. So slow down to get it right.
BEVEL & CURVE
To go from blank of steel to a carving tool blade, you need to shape a cutting bevel. You can do this with files or a small grinder. A grinding wheel in a rotary tool, like a Dremel, works very well here, as you can see in Figure 1 at right. Another option is to use a narrow belt sander.
This isn’t your final cutting edge, so your focus is on establishing the bevel, not creating a razor-sharp edge.
To add the curve to the bevel side of the blade, gently form it with hammer blows over the horn of an anvil, an iron pipe clamped in a vise, or around the curved top of the jaws of a machinist vise, as in Figure 2.
Once again, take your time here. You want to avoid workhardening the metal with too many heavy blows. This can lead to the blade becoming brittle and breaking.
HARDENING THE BLADE. The bevel you formed will cut wood at this point. (Or yourself, so watch it.) The problem is the blade won’t hold that edge for long. What’s needed is to transform the blade from soft(ish), annealed steel into a hard tool.
To add toughness, heat the blade with a torch until it’s bright orange along the cutting edge, as in Figure 3. You can do this with a propane torch. Though I find that a MAP gas torch works quicker and helps you heat the entire blade more uniformly.
Clearly, the blade is gonna get hot, so hold it with locking pliers to keep your hands safe. I like working in a slightly darkened room to better monitor the color of the blade as its heating.
Once you’ve reached an even color, it’s time to lock in the hardness. This is done by quickly quenching the blade in oil (Figure 4). That’s what the “O” in O1 steel stands for, “oil-quenched.”
Chris likes using a can of old
Grind the bevel. You can use either a rotary tool with a grinding wheel, a selection of files, or a narrow belt sander.
Heat it. Sweep a propane torch back and forth along the cutting edge of the blade until it glows uniformly orange.
motor oil for this, but even cooking oil (like peanut oil) will work. Swirl the blade in the oil until it has cooled off.
Quenching makes the blade quite hard. The downside is that it’s now brittle and tough to sharpen. What we want to do at this stage is to dial back the hardness, while making it tougher. So let’s head to the kitchen.
HEAT TREATING. Step one, warn the household that you’ll be hardening tool steel. The process creates an aroma. It isn’t bad per se, but not everyone may be a fan. Preheat the oven to 350°. Place the blade in the oven for
Cap it. Gently hammer the blade over a curved surface such as the horn of an anvil or the curved jaws of a vise.
Quench it. Dip the blade in a can of used motor oil. Finish by heating the blade in a 350° oven for two hours.
two hours until it takes on a uniform straw color. Then remove the blade and allow it to cool.
SHARPENING, PHASE TWO. If you look closely, you can see that the blade still has the grinding and file marks from the initial shaping. You can polish and refine the face and bevel of the blade until you run out of patience. Sharpen the edge, too.
We’ll leave the final sharpening and honing until after the blade is mounted to the handle. The completed knife is easier to hold for honing and you have a better sense of how sharp it is with test cuts.