EDU: How to forge your own Katana.
So since this is an armory of sorts, here's a short article on the basics of how to forge your very own Katana. Yes you! You can do this! It's actually pretty difficult, so I don't really think you could ACTUALLY do it, but it's probably some cool information for you to know. Have I ever made my own katana? No. I don't have the time/patience for it. I have made small blades though as they take a significant amount of less time to make. That and I don't have the patience to sharpen a 27" blade.
- A forge (really important, can't do it without this thing)
- Some sort of steel (we'll get into this in a bit)
- Forging hammer (kind of important too) or a hydraulic press
- Various things to keep yourself from getting burned/mauled
- A phone in the event you get seriously injured (only partially joking)
- A pair of heat resistant tongs to hold the steel
- A large anvil
First things first, traditional japanese swordsmiths forged their own steel, but that is FAR beyond the scope of this article and truthfully, I'm still not 100% certain as to how they do it, but I'm sure it takes a ton of work. So unless you can form your own pure steel into a bar, I would suggest using a piece of 1050 high carbon steel. Pick your dimensions as you want, but generally your typical Katana will be about 36" in length or 91.4cm. 27" of blade and 9" of tang. So, if you need a basemap of where to start, I'd suggest 1" wide X 3/8" thick X 30" long. Why cut it short? Because the steel will spread out.
So first things first is to make your sword-blank, or sunobe as the Japanese call it. This process is arguably the most difficult process, as it's one of the more time-consuming parts. This is what you see in the movies when you see those guys with their tongs banging on the blades. It's much more difficutl with a katana because it does silly things like it tapers not only from the spine of the blade to the cutting edge, but also from the middle to the tip and from the middle to the tang. Think of it as a really stretched out football... kind of. Companies like Paul Chen use a machine that presses the steel into a sword blank. Unfortunately, I doubt anybody has one of these as they are several hundred thousands of dollars, so looks like you'll have to be using the good ol trusty hammer. This is a trial and error part, you'll have to do it until you know how much the steel stretches and how much steel you have to work with. There's no real set of "This is how much it'll stretch" because, well I don't know how hard you hit and how well you know how to work with steel.
Dip the sword in the forge until it's red hot, pull it out work on one side, put it in and repeat. Equalize the work, do one side, then the other. It'll take the "Oh ****" factor out later when you realize your blade is asymmetrical like Paris Hilton's face. The sword-blank is extremely important. Japanese smiths will run water over the anvil and constantly dip the hammer in water as it'll get out pits and impurities in the metal when the steam is violenty created (see, whoever said violence does nothing is wrong) by the hot steel, the hammer and the water, this is also known as "wet-forging".
After this is done, it's time to move from sword-blank to actual blade. Generally, you start with the tip. The sword blank will most likely look like a long rectangular object, so you'll have to start hammering and forging the tip to the way you want it to look like. Single bevel swords are the easiest to do. You just have to hammer it out to shape and be careful not to hit too hard or you'll ruin your whole project. This part is the most awesome, you stick your blade in your forge (it should be about 2000-2200 degrees) and work the bevels quickly. Constantly check for a correct alignment. Do it in sections, it'll be easier. Once you finish hammering out the bevel of the blade, you'll have to hammer the top notch. This is the part where the tang ends and the blade begins, it's that small 90*ish angle that sits there right before the blade. This part is easy if you have a press, if not, hold with one hand and hammer away... carefully.
Now that the hardest part is out of the way, grab a cold one, take a break and get ready for some precision work. Next is making sure the blade is straight and correcting anything that you messed up on. Irregularities, bends, hammer pits, etc. Also known as the correction phase. Phew! That's a lot of work.
So now you should have what looks like a really dirty steel looking sword. Next is heat-treating. This part is crucial to how well your blade will work. Knifes must be hard and sharp and swords must be tough, but not hard. This process is called normalization. To get 1050 High Carbon steel to normalize, I'd treat it to about 1600* (also known as steel's "critical" point) and let it air cool. Do this a few times to get the grain to normalize. After this, you get to shave off all the scale that has formed on the blade. People use grinders, sand paper, blocks of stones, etc to do it. Whatever you do, it doesn't matter, just get the stuff off. Doing it by hand with a stone block allows you to get ripples and other imperfections out much quicker.
Next is where the genius and legendary-ness of the katana comes from. It was ingenious the way the Japanese came up with this technique. What they did was coat the spine of the blade in clay, leaving the edge exposed. Doing so makes the edge hard and the spine soft. Because when steel heats, it forms into crystaline structures at certain temperatures. There's a lot about it, but beyond the scope of this article. So coat the spine in clay, leaving the edge exposed, dip into forge until about 1500*, then quench in water. This part is the deal breaker. If you heat it too much, the blade will crack, if you don't heat it up enough, it'll not harden and if you hit something it'll break. Steel loses it's magnetic properties at it's critical temperature point. So seeing if it's magnetic is usually an indication of when it's time to drop it in the water.
Once this has been done your blade will take up quite a curve on its own. Afterwards, comes the tempering. Tempering and hardening are always confused. Tempuring relieves the stress on the steel and makes it less brittle. This is usually done in hot oil baths at around 400* F and at 3, one hour, cycles.
You're ALMOST done. Next is to sharpen and polish the blade. This part is very demanding and very time consuming. The traditional method is to use a grinding stone to profile the blade and get the oversized edge correct, once you've done this, it's time to sharpen. Starting off with about 180 grit japanese sanding stone, you will progressively move up on the higher grits until you can see your face in the blade. As you profile the blade with the stone, you'll move from profiling to polishing, though at which point this happens, it's not really known as you'll be too focused and bored out of your mind to realize it. What you're trying to do is to get the edge visible. Usually you'll go up to about 2000 grit before you're done. After that buff and wax and polish.
You'll end up spending about 40-60 hours doing this. So it's not something you can knock out in an afternoon. My friend's blade took him about 3 months to do. My 4" knife took me about 3 weeks to do, but it broke because I was a n00b. There are a lot of things to consider when actually doing this and one must have a pretty decent hold on the knowledge of steel and how it works to make a really good blade. Otherwise, this is just some fun stuff to know.
- Get steel
- Make sword blank
- Hammer down for bevels and correct shape
- Correct any problems, pits, shape, straightness, etc.
- Make blade
- Heat treat
- Polish and sharpen