page_title: Japanese sword
section_title: Manufacturing
hierarchical_section_title: Japanese sword / Manufacturing
context_page_description: A Japanese sword is one of several types of traditionally made swords from Japan. Swords have been made from as early as the Kofun period, though most people generally refer to the curved blades made after the Heian period when speaking of "Japanese swords". There are many types of Japanese swords that differ by size, shape, field of application and method of manufacture. Some of the more commonly known types of Japanese swords are the katana, tsurugi, wakizashi, odachi, and tachi.
context_section_description: Japanese swords were often forged with different profiles, different blade thicknesses, and varying amounts of grind. Wakizashi, for instance, were not simply scaled-down versions of katana;  they were often forged in hira-zukuri or other such forms which were very rare on other swords.
  The daishō was not always forged together. If a samurai was able to afford a daishō, it was often composed of whichever two swords could be conveniently acquired, sometimes by different smiths and in different styles. Even when a daishō contained a pair of blades by the same smith, they were not always forged as a pair or mounted as one. Daishō made as a pair, mounted as a pair, and owned/worn as a pair, are therefore uncommon and considered highly valuable, especially if they still retain their original mountings (as opposed to later mountings, even if the later mounts are made as a pair).
  The forging of a Japanese blade typically took weeks or even months and was considered a sacred art. As with many complex endeavors, rather than a single craftsman, several artists were involved. There was a smith to forge the rough shape, often a second smith (apprentice) to fold the metal, a specialist polisher (called a togi) as well as the various artisans that made the koshirae (the various fittings used to decorate the finished blade and saya (sheath) including the tsuka (hilt), fuchi (collar), kashira (pommel), and tsuba (hand guard)).  It is said that the sharpening and polishing process takes just as long as the forging of the blade itself.
  The legitimate Japanese sword is made from Japanese steel "Tamahagane".  The most common lamination method the Japanese sword blade is formed from is a combination of two different steels: a harder outer jacket of steel wrapped around a softer inner core of steel. This creates a blade which has a hard, razor sharp cutting edge with the ability to absorb shock in a way which reduces the possibility of the blade breaking when used in combat. The hadagane, for the outer skin of the blade, is produced by heating a block of raw steel, which is then hammered out into a bar, and the flexible back portion. This is then cooled and broken up into smaller blocks which are checked for further impurities and then reassembled and reforged. During this process the billet of steel is heated and hammered, split and folded back upon itself many times and re-welded to create a complex structure of many thousands of layers. Each different steel is folded differently, in order to provide the necessary strength and flexibility to the different steels. The precise way in which the steel is folded, hammered and re-welded determines the distinctive grain pattern of the blade, the jihada, (also called jigane when referring to the actual surface of the steel blade) a feature which is indicative of the period, place of manufacture and actual maker of the blade.  The practice of folding also ensures a somewhat more homogeneous product, with the carbon in the steel being evenly distributed and the steel having no voids that could lead to fractures and failure of the blade in combat.
  The shingane (for the inner core of the blade) is of a relatively softer steel with a lower carbon content than the hadagane. For this, the block is again hammered, folded and welded in a similar fashion to the hadagane, but with fewer folds. At this point, the hadagane block is once again heated, hammered out and folded into a ‘U’ shape, into which the shingane is inserted to a point just short of the tip.  The new composite steel billet is then heated and hammered out ensuring that no air or dirt is trapped between the two layers of steel. The bar increases in length during this process until it approximates the final size and shape of the finished sword blade. A triangular section is cut off from the tip of the bar and shaped to create what will be the kissaki. At this point in the process, the blank for the blade is of rectangular section. This rough shape is referred to as a sunobe.
  The sunobe is again heated, section by section and hammered to create a
caption: Cross sections of Japanese sword blades showing lamination types.