I’m working on a threesome of knives for a customer, and I’ve been sending him picture updates as I make progress. Since I’m taking progressive pictures, I decided to take the opportunity to do a progressive thread showing the steps I go through in building a knife.
The first thing I do is draw out my ideas on paper. You can see the paper in the top of the pic. After I get a good idea of where I’m going with the design, I transfer the design to my raw material with a sharpie marker. These particular knives are made out of some of the customer’s grandfather’s farrier rasps. Grandpa was a farrier, and my customer wanted something with that heritage. He wanted three knives that were alike, but subtly different.
After I get the designs on the raw material, I use an angle grinder to cut off the big pieces and my belt grinder to finish the profile. When they’re done, they look like this. I had started grinding the bevels on the top one.
Once the knives are profiled, it’s time to grind the bevels. These knives are all going to be flat ground most of the way up the spine. I grind the bevels with a 60 grit belt, then switch to a 120 and then a 220 to get them ready for heat treating. When they’re ready to heat treat, I drill the handle pin holes. Don’t forget to drill the pin holes before you heat treat, as hardened steel is tough on drill bits, if it will drill at all. Learned that one the hard way.
Once they’re ground and machine polished, it’s time to fire up the forge. My forge is literally a pile of bricks and some charcoal. Forced air from an air mattress pump is blown under the fire through a pipe called a tuyere (tweer). The materials are simple, but it takes practice to learn heat control.
You can see in the picture how the knife is showing some color. It looks like dark red in the picture, but it’s more like a red in natural light, or like a dark orange at night. The simple version of what I do is to take the knife to nonmagnetic and then quench it in oil. There’s more to it than that, as I normalize at least twice before the quenching heat, and I pay careful attention to not overheat the blade, particularly the tip. When the heat is nice and even throughout the blade and I see the color I want, I quench the blade. There are many quench mediums available, anything from waxy goop up to fancy quench oils that cost 25 dollars a gallon and more. I use vet grade mineral oil, a light thin oil, and it gives me results that I’m satisfied with. To me, my results are better than are available using goop, dirty motor oil, or vegetable oil.
Coming out of the quench, the blades are very hard, but brittle. If I were to whack one on the side of my anvil, it would shatter. In order to take care of the brittleness, the knife is tempered. I like to temper at 450 for two one-hour cycles, shooting for a Rockwell hardness in the 58 to 60 range. You’ll notice in the picture that the knives are silvery gray. That color is one of the indicators that the heat treat went well.
When the knives come out of the oven, they have interesting colors. You may have read about tempering to a “dark straw” color. The blades in the picture are purple. When you wash and scrub the oil off of your blades, which you won’t forget to do more than one time, and put them in the oven with forge scale still on, the scale holds a little of the oil and makes the colors darker. When you sand off the scale before you temper, you get….you guessed it, dark straw.
After tempering, I take them back to the grinder. I grind the scale off with a fresh 220 grit belt, then polish them up with 320 and 400. When the 400 grit finish is nice and even, it’s time to start hand sanding. Some people find hand sanding relaxing, others tedious. Either way, it’s the best way to get a nice even finish. Someone once told me to use sandpaper as if it were free. You’ll only frustrate yourself and take more time by over-using a piece of paper. I like the Norton paper, and the 3M comes well recommended. The cheap stuff from Harbor Freight is cheap for a reason. If I took the blade to 400 on the machine, I start hand sanding at 320. I use WD 40 as a cutting fluid.
That’s my brother sanding. You may notice that he’s using a block of wood to back the paper. A hard backing makes your paper cut better and last longer. I use 320, then 400, then 600. When you switch grits, change directions. Think ahead so that your final grit runs parallel to the blade. When you get your 600 grit finish nice and even, clean off the blade and get a fresh piece of 600. Run it in smooth lengthwise strokes the entire length of the blade. This makes a good working finish with no “fishhooks.” Take one side all the way to finished before you start the other side. Tape up the finished side before you put it back in the vise, so you don’t scratch it.
The picture above is the machine finish on the second side, after I finished the first side. When the second side is done, tape the entire blade. Cut your handle material roughly to shape and drill the pin holes. Leave your pins a bit long, so they stick out the sides of your handles. You only have to profile the front edge of the handle prior to gluing, but get that front edge down to at least 220 grit. I use 2 part 60 minute epoxy. Glue the handles, and clamp lightly. The strength of the joint is in the glue, and if you clamp too tightly, you’ll squeeze too much glue out.
After the glue cures overnight, it’s back to the grinder for profiling. The scales on this particular knife were extra thick, so it took a while at the grinder to get them profiled. Fresh belts cut quickly, and old belts don’t cut as fast. Keep that in mind. As you get closer to where you want to end up, switch to an old belt so that the inevitable “oops” won’t be as bad and will be easier to fix. When you’ve got it just about profiled, you can switch to a finer belt, or you can go to hand rasps and files for even more control. When you’re satisfied with the profile, take the handle down to at least 220 grit. This one went to 400. I use a super glue finish on most of my handles. It takes at least 4 coats, sometimes 8, to get a nice even finish. Sand smooth to 220 or higher in between coats. I use a single finger from a latex glove, because super glue will stick your appendages together. I use cheap dollar store super glue, as the thinner glue makes a better finish.
After the handle is finished, all that’s left is to sharpen the knife, etch my name, and take pictures to get it ready to sell. I forgot to take pictures of the etching process. I’ll catch it on the next round and put pictures up. Specs on this one: 13 inches OAL, handle material is paduak, with three 3/16″ brass pins.
I finally finished two more of the knives from this thread. The one on the left is about 11 3/4 inches with cocobolo handles and six 1/8″ brass pins. The one on the right is 11 1/2 inches with bubinga handles and two 3/16″ brass pins.