Japanese Sword Arts FAQ Version 2.7
9. How is a Japanese sword constructed?
Seriously, there are as many as a half-dozen people involved in the construction of a sword.
The swordsmith forges the actual blade. He starts usually with a special kind of traditional Japanese steel called tamahagane, and works with hammer and forge to fold it a number of times. There are two processes in general, one to make core steel (shinganae) and the other to make jacket steel (kawagane). Kawagane is folded more times and ends up being harder and less ductile than shinganae. In the most simple construction, a piece of kawagane is folded around a piece of shinganae to form a jacketed core. Thus the shinganae allows the sword to flex instead of breaking on impact, and the kawagane allows it to take the famous razor edge. More complicated construction methods can produce swords made of as many of 5 pieces of steel, all forged differently.
The folding process is used to closely control the uniformity and carbon content of the steel. An accomplished smith can tell by eye to within a tenth of a percent the carbon content of a piece of steel.
When the basic blank has been constructed, the smith will continue to work what is essentially a metal bar into the shape of the sword. When the forging is done, the blade is the correct length, curvature and general shape, but lacks a finish and certain of the various edges and features. The smith will then use coarse polishing stones to further define the blade before passing it onto the polisher.
The polisher uses successive grades of stone to finish the blade. The polisher is responsible for the famous edge, but that is only one part of his job. His real job is to bring out the beauty of the smiths art. Properly polished, the complexity of the construction is revealed. Improperly polished, the blade is ruined.
A woodcarver makes a saya (scabbard) for the sword. Each saya is custom carved out of wood from the ho tree. The actual blade is required, as the carver will use it as a template to make a properly fitting saya.
A jeweller makes the habaki, the small but critical metal piece which is constructed to fit exactly on the blade next to the tang, and provide the snug friction fit which keeps the blade from rattling in the saya.
Further craftsmen make the finishings. There can be separate craftsmen for the tsuka (handle), tsuba (handguard) and menuki (hilt ornaments).
9a. How many layers in a Japanese sword?
It depends on the smith. Shinganae is generally folded about 10 times, resulting in about a 1000 layers. Kawagane is folded anywhere from 12 to 16 times, depending on the smith and the metal he is working with, and so could have from 4000 to 65000 layers.
9b. What are the different types of Japanese swords?
Generally, the swords are classified by length. A daito is a sword with a blade longer than two shaku ( shaku = 11.9 inches ). A wakizashi is between one and two shaku in length, and a tanto is less than one shaku.
There are lots of other names. The most common one, katana, refers to the style most people have seen, a daito which is worn stuck through the obi (belt) with the edge up. A tachi is an older style, slightly longer and more curved, worn slung on cords with the edge down, usually used in a calvary style. A nodachi is a bigger tachi, with a very long handle, worn slung over the back for battlefield application. A kodachi is a smaller tachi. A wakizashi is also a short sword, although of a newer style (kodachi is often used as a generic term for short sword, and so may also be used to refer to a wakizashi). A chokuto, or ken, is a very old style straight sword.
9c. How is a Japanese sword measured?
The length of a Nihon-To is measured from the back of the tip in a straight line to the mune-machi (which is where the back of the blade fits into the habaki). Since some blades have more or less sori (curve) than others, the measurement is done in a straight line for simplicity and commonality. A sword with a lot of sori would be actually longer if you followed the shinogi, for example, than a sword without much sori. But in the final result, they both reach the same distance away from the swordsman. The handle is not included because it doesn't matter how long the handle is.
For record keeping purposes there are several different measurements made on the blade to give a more complete description. Besides the length of the blade, the length of the tang is measured, the width of the blade at the machi (where the blade meets the tang), the width at the yokote (defining line between tip and blade), the thickness at the mune machi and the yokote, and the length of the kissaki (tip).