Kobold Press

Real Steel: The Katana

KatanaThe katana is a bigger-than-life weapon with a long and colorful history. It is surrounded by so much legend and mystery that it is sometimes difficult to get to the truth. In the previous article we discussed tamahagane, the steel from which traditional katana are made, and before that we talked in some detail about heat-treating. Now, let’s take a look at the making of a katana from forging to heat-treating and polishing—then perhaps a bit on use.

Keep in mind that I am not a traditional Japanese swordsmith, and this is not necessarily how I would go about making a katana. Techniques vary from smith to smith, but you’ll get the idea.

The Pre Form

The first step is forging the tamahagane billet into a pre form called a sonobe. The billet is drawn out to roughly the correct length, width, and thickness — with a little extra metal left in each dimension to allow for manipulation. This process is quite laborious when done by hand, and today even traditional smiths usually use a power hammer to get through this stage. This has no bearing on the quality; the modern labor saver allows the smith to devote more time to the final details including the final hand forging…

bare bladeForging the Blade

After the sonobe is complete, the blade can be forged closer to its final shape. The tip is usually forged first, by striking down and in at about 45° with strong hammer blows. Interspersed gentle hammer blows at varied angles make the tip, or kissaki, rounded rather than flat or chisel shaped. The bevels are usually forged next.

Katana have a single bevel on each side of the blade that runs from the spine of the blade all the way to the edge, as opposed to western blades, which generally have primary and secondary bevels. Although the blade is flipped over and worked on both sides, the anvil shapes the bottom of the blade as the hammer shapes the top.

As the bevels are forged, the blade is forced back, curving away from the edge and toward the spine. This curvature is called sori and must be corrected for by straightening the blade periodically during forging. (Although the katana is a curved sword, you’ll see shortly why it can’t have too much sori when it gets heat treated.) After the bevels are formed, the tang, or nakago, is forged.

When forging is complete, the blade is rough ground using coarse stones and files to remove the iron oxide forge scale as well as to enhance the shape.

Heat Treating

As we discussed in the article on heat-treating, here’s where the magic happens. A mixture of clay and ash is skillfully applied to the blade and allowed to dry. The blade is heated to critical temperature and then quenched in warm water. This is a time of great angst for the smith since a lot of effort has been expended in forging this blade, and a high percentage of water quenches destroy the blade. As the blade is quenched, the smith will either feel a subtle vibration in the tongs as the blade sings to its maker that it is born or a nasty jerking accompanied by an audible ping: a sure sign that the blade has cracked and did not survive hardening.

In that fraction of a second, a lot happens in the quenching blade, but the one thing that can be seen is that the blade first curves down, and then up, resulting in the final curvature. The blade emerges from the quench with considerably more curvature than it entered with. Generally, an oil-quenched blade curves down and stays that way, so an exaggerated curvature has to be forged in before quench. Also, oil quenching is far less deadly to blades than water, but arguably also has a couple of disadvantages. Check out this video to see what happens during a water quench.

The clay coating protects the spine from rapid cooling and results in the spine being softer than the edge, yielding a tough and flexible blade with a hard edge capable of excellent edge retention and great sharpness. It also produces an amazing effect called a hamon. Ha means edge or blade, and mon translates to badge, so hamon is the badge of the blade. It is the physical border between the softer pearlite spine and the hard martensite edge. It is visually beautiful and can appear as clouds, mountains, the moon, or wisps of smoke. The creation of hamon is considered an art in and of itself.

hamonAfter quenching, the blade is tempered. Traditional tempering is accomplished either by drawing the blade across a hot block of metal until it is sufficiently drawn back, or softened, or by placing the entire blade in the forge and quickly removing it until the desired temper is reached. The smith watches for the steel to change color as an indication of its state of temper. Oxides form on the surface of the steel and go through color phases: from yellow through orange, brown, blue, and purple as the metal becomes softer but tougher.

Polishing

The last thing done before the blade is mounted is polishing. Although western smiths often sole author a katana, doing everything from forging (some even smelt their own steel) through mounting, a traditional Japanese smith will usually have the blade polished by a specialist. The process starts with relatively coarse bench stones and progresses through increasingly finer grits until the final stages are accomplished with very fine finger stones. Very small areas are worked with the finger stones pinched against the blade with the thumb and index finger. The polishing not only yields a mirror surface, enhancing the hamon, but also creates the final edge geometry and gives the blades its final edge.

It’s a Cutter

Depending on blade shape and geometry, swords can be primarily for thrusting or cutting. Cutting swords can be further divided into hackers and slashers. A gladius, for example, is a hacking and thrusting sword; the cuts are percussive. The katana is a slashing sword that is also pretty good at thrusting. Slashing cuts are also called draw cuts: the sword is pulled in through the cut. The highly polished surface of the blade helps it pass through the target, as does the subtle wedge-shaped geometry.

What’s Real?

“I heard that Japanese soldiers during WWII disabled machine guns by cutting off the barrels with their katana.” Definitely didn’t happen. Although some steel blades can cut steel, it’s done with a band saw and takes some time. No sword has ever been made that can cut through a machine gun barrel. If your Great Grand Uncle Grumpas told you he saw this happen, with all due respect, he’s mistaken.

“I heard that katana were heat-treated by heating them and stabbing a slave or convict.” I can’t say for sure no one ever tried this, but I can tell you it won’t work. Organs and body fluids cannot carry the heat away fast enough to harden a blade.

“I heard katana were tested by cutting through corpses and received designations, such as one-body blade, two-body blade, etc.” True.

“I heard katana were tested by cutting through live convicts and received designations, such as one-body blade, two-body blade, etc.” Probably true.

“I heard katana are unbreakable.” Definitely not true. The katana is a delicate 3-ft.-long razor blade. Despite the clay hardening process that toughens it, repeated blade-to-blade and blade-to-armor contact quickly leads to chipping and eventually to breakage. This is why so few antique katana in decent condition exist today.

10 Replies to "Real Steel: The Katana"

theeo123

October 21, 2010 at 3:50am

Ive had a keen intereste in japanese swordsmanship over the years. anyone who really wants to learn more about the process,s of making the katana, or the history around it, and it’s use should start here.
http://www.bugei.com/
The company, makes real folded katana’s forged, by hand in the traditional sense, as I recall their smith, is a 4th generation smith. the site is very informative, and spends a lot of time trying to educate rather than just sell blades. check out their articles, and alo the books/video’s the sell concerning the history of the blade.

nermal2097

October 21, 2010 at 4:36am

Excellent, very informative and I loved that video clip. Will you be covering the mounting of a blade in a future article?

Todd the Bladesmith

October 21, 2010 at 5:21am

@theeo123 – I also endorse Bugei for anyone who is in the market for a high end hand made production sword. I recommend CAS Hanwei for those who want a good quality sword on a budget.

For those wondering why I would send you to someone else for a sword, I’m not currently taking orders for long swords of any kind. I am taking orders for short swords, wakizashi, and of course knives, including tanto. I plan on taking long sword orders starting next summer.

Thanks for the input!

@nermal2097 – Although you and I are very interested in mounting I’m not sure others would be. Because of that, and the sheer number of skills and steps involved, the best I can offer you is a weak maybe. Time (mine) allowing maybe this is something we can talk about on the forums…

thorr-kan

October 21, 2010 at 6:49am

Another cool and informative article.

Lucas Jung

October 21, 2010 at 3:47pm

@theeo123 & Todd the Bladesmith:

I hate to break it to you, but Bugei do not sell quality swords. A sword isn’t necessarily inferior just because it wasn’t forged in Japan, and there are smiths outside of Japan who make swords that are arguably of comparable quality to Japanese swords–Bugei are not among them. They are not even in the same neighborhood as the “high end.” They have a very snazzy website full of convincing-sounding “facts,” but in reality they’re selling second-rate overpriced knockoffs.

If you want a sword which will appreciate in value as a collectible, your only option is a Japanese-forged shinken (true sword). They’re not cheap. By “not cheap,” I mean, “The lest expensive ones cost half as much as a new car.” If you want a forged/folded sword of good quality but don’t care about its value as a collectible, there are far better options than Bugei (you can get a sword that is higher-quality than anything Bugei sells, sometimes even for a lower price).

Whether you’re looking for a collectible or just a practice sword, the best source in North America (and Europe, for that matter), is:
http://www.swordstore.com
They sell Japanese shinken for collectors. Also, if you’re not a collector but just want a well-made forged/folded sword, check out their “Steel Iaito.” They’re of higher quality than anything Bugei sells, but unlike Bugei they don’t pretend that they’re the real deal.

Todd the Bladesmith

October 21, 2010 at 4:15pm

@thorr-kan – Thanks, that’s what we’re shooting for!

@Lucas Jung – We’ll have to agree to disagree about Bugei. Note that I did say high end “production” sword. I’m not a huge fan of production swords in general, but Bugei can put a solid tradionally built sword in your hands for under $2,000, and CAS Hanwei can do it for under $200 (non tradional construction and materials, though). As production swords they won’t be as good as a custom, whether it’s by an American smith or it’s a genuine Nihonto. Bottom line is the vast majority of people can’t afford to spend thousands, and these companies provide functional swords for much less.

I also have to disagree about a sword having to be Japanese made to appreciate in value. Swords by Don Fogg, Howard Clark, Rick Barrett, Walter Sorrells, and Jesus Hernandez, to name a few, all sell for a small fortune. Heck, Howard Clark makes katana from L6 bainite that regulary go for $12,000 and have done nothing but appreciate – and L6 bainite isn’t exactly tradional steel.

Thanks for the comments, Lucas!

Lucas Jung

October 21, 2010 at 4:34pm

@Todd:

My main objection to Bugei is that they make every effort to create the false impression that their swords are in the same league as traditional Japanese swords (i.e. shinken), especially by using misleading verbage like “traditional.” Swordstore.com also sells “production” swords (the aforementioned “steel iaito”) for less than $2,000, but they are very up-front about what they are selling, going out of their way to differentiate them from the genuine articles. From the perspective of a practitioner, they’re also clearly superior in quality to anything sold by Bugei.

I was completely unaware that people were collecting non-shinken. When I think about it in terms of the things that give shinken their value, the idea of non-shinken appreciating in value is almost completely inconceivable. Then again, collecting is all about perceived value, so I shouldn’t be all that surprised that people are collecting non-traditional swords, especially if they are made in novel ways (e.g. bainite). Thanks for showing me the blind spot I had here!

Todd the Bladesmith

October 21, 2010 at 5:22pm

@Lucas – I must plead ignorance to Bugei’s business practices, but I’ll certainly look into them further before I recommend their swords again. I’ll also be looking into Swordstore.com further. I wish I could just send everyone interested in a katana to one of the smiths I know who make great swords, but like we both have said, the prices are in a range that make them unrealistic for most.

The market for American made Japanese style swords is growing every day. Japanese master smiths now take on Western students and Western smiths train each other, and are creating our own unique styles. It’s a good thing, Lucas, and I encourage you to look at the work of American smiths when next you’re looking to buy a sword.

Ardashir

October 21, 2010 at 7:30pm

Great and very informative article, and the links posted by the other commenters look interesting as well.

Todd the Bladesmith

October 24, 2010 at 7:44am

@Ardashir – Thanks, and ditto on the links. Input and friendly discussion are always welcome here.