Well folks, I finally got to take my knife making class and I can say that it was, without a doubt, worth the money.  The instructor was Rachelle up at Trackers Earth – Portland and, like before, she was a wealth of information. As usual, I was brimming with questions which have absolutely nothing to do with the class and she answered all of them, which I appreciate.  In my opinion, there isn’t enough accurate information out there on why we use what we use to make a forge, so I took advantage of the opportunity to learn as much as I could in between actual knife-making lessons, demonstrations and my own blade work.

Something I encounter often online are various ‘DIY’ instructions on how to make a propane forge. Lets talk about a key concept of a forge – reaching and maintaining temperatures high enough to soften the metal you are working with. It may surprise you to know that most of the high temperatures inside a forge aren’t primarily the result of conduction or convection (the heat from the forge walls or the flames themselves), but is rather a cumulative, reflective heat from your refractory material.

Quite literally, you can make a forge by having a non-flammable surface to put your forge on, a bunch of fire bricks (roughly $3.50 each at the store) stacked in a box configuration, and a propane jet you can make from supplies at the hardware store.  That is really all you need to get started.  This, however, is not the most efficient forge in the world and it may not get hot enough to do some of the things you may want to do, like forge weld.  To bump up the heat, you can do many different things, which I am listing here in order of increasing cost.  First, you can add insulation to the inside of the forge, like Kaowool. Kaowool is a fibrous insulating material that comes in sheets and can easily be molded/cut to fit any shape.  If that doesn’t get your metal hot enough, you can paint the Kaowool with a reflective high-temp paint called ITC-100, which will reflect up to 98% of the heat that hits it (it also has a side benefit of reducing the amount of fiber dust that comes off of the Kaowool).  Lastly, you can always add more jets and/or you can buy better jets.  Buying high end jets will allow you to dial in airflow with a choke and are designed to be very efficient so you will also save on fuel.  The cost of some of these jets can be quite high, though (~$200 each).  If you want to have a case around your forge, that is something that may add stability and protection, but doesn’t really add much to your ability to heat up a piece of metal.

This, of course, assumes you are using propane.  If you want to use coal, the setup is even easier. I will be making a coal forge at some point, but right now I am focusing on improving the forge I have.  Now that you have a forge that will get metal to the proper temperature, the first thing you want to do is make an implement of destruction – like an axe or a knife (not the best idea as there are some basics you need to learn before you do that).  Once you have gotten a piece of metal into the shape you want it, you have to make it battle ready.  To do that, you have to heat treat it to get it hard enough to cut and resist bending, but not so hard it shatters when it strikes another object.

Heat treatment is an important part of any tool making process.  Yes.  Knives, swords, axes, hammers, and all the rest of the things you can destroy stuff with are tools.  I won’t get into metal selection, because there are a lot of factors that can determine which kind of iron/steel to use for specific purposes. If you want to read about it, here is a forum thread that talks about choosing your steel.  The four basic heat treatments are annealing, normalizing, hardening, and tempering.

Annealing is the process of softening the metal you are working with.  I know, you are asking yourself why you would need it softer.  Making the metal softer allows the potential energy that is bound up in the metal molecules to relax.  You spent hours banging on this thing and now it is like a stretched out rubber band down in the bonded molecules.  Getting slammed against something can cause these stretched out bonds to snap and may result in micro fractures in the steel or outright breaks.  To relieve the stress, you anneal the metal.  You get the steel up to the temperature at which it loses magnetism (test by holding a magnet up to it outside the forge – this is referred to as the “curie point”) which is somewhere between 770F and 1390F for mild steel. At this point, you shove the metal into a non-flammable insulating material until it is completely covered, where it will cool slowly over two (or more) hours.  The material we used is called “vermiculite” and it was commonly used to insulate houses until different insulators were discovered. Once the metal has cooled enough to handle it comfortably, you can use a belt sander or grinder to refine the profile (edges) of the knife and grind out all the hammer marks on the sides. At this point, you need to make any holes you’ll need later for handle pins and refine any bevels that you roughed in during forging.  Basically, when you are finished with this step your knife should be near what you want it to look like at the end.

Normalizing is pretty much the same as annealing, but it doesn’t make the metal quite as “soft” and you cool it by setting it aside in the open instead of enclosing it in an insulating material.  The annealing step of heat treatment can be exchanged for normalizing, depending on how soft you need the metal to be to accomplish your goal.

The next step in the heat treatment process is hardening. When you harden a piece of steel, it gains the ability to have a sharp edge, but it also becomes brittle.  To harden the metal, you heat the steel to between about 1450F and 1500F, then take it out and quench it in oil for 8 to 10 seconds (moving continuously).  When you quench in the oil, hold it by the tip of the handle and move it in a thrusting motion into and out of the oil and attempt to only harden the bladed parts of the knife. This keeps the spine flexible while hardening the blade and ensures that both sides of the knife are exposed to roughly the same temperature of oil.  Moving the knife side to side would cool one side faster than the other and may result in warping.  Once the metal has been hardened, you must quickly move to tempering.

The tempering process can be done one of two ways and the temperature at which you temper the metal will depend on how hard you want it versus how flexible you need it to be.  There are a lot of places where you can find that particular information for a variety of blades and uses, so I am going to just go over a basic knife made with mild steel.  In the first method, you heat an oven up to 390F, put the knife in for an hour, take it out to cool to room temp, then repeat this process two more times.  This will reduce the hardness slightly, but will reduce the brittleness greatly. Increasing the temperature at which you temper the steel will result in increasingly less brittleness, but also increasingly less hardness.  An alternate to using a normal kitchen oven (which is also much faster) is to clean a spot on the metal, observe the metal while holding it in front of the forge heat until it turns a gold/bronze color (specifically along the blade), then quenching it in/out of water quickly one time. You repeat the process two more times to complete the tempering.  The steel will turn gold/bronze as it hits roughly 390F and doing a quick quench lowers the heat without allowing the metal to warp.  Once this process is complete, you will have a nearly complete knife blade.  To finish out the knife you do a final grind (keeping in mind the metal is now harder than it was during the first grind) and/or polish, make and attach the handle, and finally sharpen.

At this point, you have a completed knife which should function pretty much like a store bought knife.  What I like about being able to hand-forge my own knives is being able to decide what metal to use, what kind of handle I want (sandwich style or guard/handle/pommel), what shape I want the blade and determining all of the minutiae that goes into crafting it – depending on what I want to do with the knife.  After having made several small knives, I can tell you that I now understand why hand-forged bladed items are so expensive – there is a lot of work that goes into making a sword or a knife. At this point, I can hammer out metal as well as anyone with my level of experience but forge welding consistently, especially big pieces of metal that need to be welded along their entire length, is still proving to be a problem.

Based on the information I’ve gathered from talking to Rachelle, watching experienced blacksmiths and through my own trial and error, I’ve come to the conclusion that my issue is less technique and far more likely a “hot spot” in my forge which which is causing significant temperature differentials.  Because of this, I am only able to get small pieces of metal up to forge welding temperature (by placing them directly into the hot spot), but not large pieces as the overall temperature of the forge isn’t getting high enough.  To solve this issue (I hope), I will be ordering some Kaowool for my forge this weekend and constructing a new burner so I can have two jets – which will not only increase the heat but also spread out the distribution inside the forge.

Eventually, I will be painting it with ITC-100 and replacing my homemade burners with some nice new ones, but this requires a bit more of an investment than I can afford right now.  Hopefully, the extra burner and Kaowool will be sufficient to get a large piece of metal to forge welding temperature.  If that doesn’t work, I will be building a coal forge for the sole purpose of forge welding as I have heard that forge welding in a coal forge is much easier than in a propane forge.  Either way, I’m going to get this done!  Waterboard and I did manage to come up with some cool little gadgets the other night.  You can look forward to seeing them available for purchase on the website as soon as we refine the process a little and come up with some standard models.  I think many of my Scandinavian culture loving friends will be very excited about these…but I’m not going to give away the surprise.  I’ll put a picture up once we have ten or twenty of them made.  I’m guessing we will have them up for around $25.