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From Value One, Summer 2010 No. 29  

Coating with miso is unique to file making.

The Nigata district of Kure City in Hiroshima Prefecture faces the Seto Inland Sea and is known as a big file production center in Japan, holding a 95% share of the national output of this item. Files are indispensable hand tools for manual craftwork. They are used to shape/smooth iron and other metals, wood, plastics, and gypsum, among other things. The history of file making at Nigata dates back to the Edo era (1603–1868). In this area, some 50 companies manufacture files today.

Files are available in a great variety. Typical ones include metal files for smoothing burrs on steel to make it ready for further processing; assorted files for finishing fine parts, such as machine molds; and double-edged files for setting the teeth of saws. Unique ones include files for cutting ski edges, surgical files for shaping/smoothing bones, and files for working on sword sheaths. There are well over 1,000 different types of files.

Files are made in a similar process to that of knives, saws, or other similar items, i.e., steel is rolled into a plate, annealed, ground, and quenched, generally in that order. However, the file-making process is more characterized by the coating of miso (fermented bean paste) that goes on the material before quenching than anything else. The purpose of this unusual step is to prevent a vapor film from forming on the surface while the material is being quenched in water. A vapor film formed on the surface would slow down the cooling speed and make perfect quenching impossible. Incidentally, many file manufacturers in Nigata bear corporate names containing the word tsubo (pot). This derives from the pot in which miso is contained.

Nigata boasts the greatest output of files in Japan, but production volume has shrunken every year after reaching its peak in the 1960s. Mr. Shigeo Kajiyama, president & CEO of Tsubosan File Co., Ltd., the biggest file manufacturer in Japan, says, "We have made whatever kind of file the customer needs. Files are a mature product, but if you search for unmet needs, you can hit on new ideas." One good example is Bright-900, Tsubosan File's innovative product whose surface is coated. Files become clogged with filings, but the coating over the gaps in the grain prevents clogging, resulting in a revolutionary file virtually free from blunting.

Files are indispensable for manual craftwork. Craftsmen in Nigata, Kure, will continue to support Japan's manufacturing industries.


Teeth are cut into a file by machine, but controlling the machine requires a high level of skill.



After heating, the file is rapidly quenched in water.




A variety of files from Tsubosan File (At both ends are Bright-900 files.)

Kure Maritime Museum (Yamato Museum)
5-20 Takara-machi, Kure-shi, Hiroshima, Tel: +81-823-25-3017
Hours: 9:00 a.m. to 6:00 p.m. (until 7:00 p.m. in July and August); closed on Tuesdays
Admission: ¥500 for adults, ¥300 for high school students, and ¥200 for junior high and elementary school students


Kure is known for the defunct Kure Naval Arsenal, which built the battleship Yamato during World War II. The naval arsenal flourished as the most important naval port in East Asia from ancient times. Many files from Nigata are said to have been used there. At the Kure Maritime Museum (also known as the Yamato Museum), which was opened in 2005, a one-tenth-scale model (about 26 meters in overall length) of the formidable battleship Yamato is exhibited. Other exhibits feature the history of Kure and its science and technology, including shipbuilding and steelmaking, which formed the basis of Kure's modernization.
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