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From Value One, Winter 2012-2013, No. 39  


Balls used for pachinko (a vertical pinball game popular in Japan) are officially known as yugi-kyu (amusement balls), and a great majority of them are manufactured in Osaka. At present, there are more than 14 billion pachinko balls in Japan. A pachinko ball—strictly defined as measuring 11 millimeters in diameter and weighing 5.4 to 5.7 grams by the National Public Safety Commission—embodies the best of Japanese steelmaking technology. One aspect of this technological excellence is heat treatment. The inner structure of a ball consists of three layers: a core made soft by tempering, a second layer hardened by carburizing and quenching, and an outer layer plated with chromium. The surface layer is extremely shock resistant, and the inner layers also absorb shocks. This makes the ball's unique behavior of bouncing when it hits a nail possible.

The first pachinko parlor opened in 1930 in Nagoya City. In those days, copper coins or medals were mainly used as the items flipped rather than steel balls. After the end of World War II, however, a large number of ball bearings made for use in military equipment during the war were diverted for use in pachinko games. pachinko subsequently enjoyed a tremendous boom as an amusement for common people enjoying the economic prosperity stimulated by postwar reconstruction demand. Manufacturers of pachinko balls also multiplied, with their number surpassing 120 in the whole country at the boom's peak. As the qualitative requirements for the product became increasing strict, however, unqualified manufacturers fell by the wayside. The Pachinko Ball Product Association now has only four member companies.

Hikari Nanotech Co., Ltd. located in Daito City, Osaka, is the leading manufacturer of pachinko balls, holding an approximately 70 percent share of Japan's market. The company is an integrated manufacturer engaged in the whole process of pachinko ball production, from the cutting of wire rods to pressing, carburizing and quenching, grinding, engraving, plating, and packaging. In collaboration with a major steelmaker, Hikari Nanotech also developed the material used—carbon steel wire rods for cold heading. The qualities of long-term resilience and durability, both vital to the quality of pachinko balls, are determined by the technical standards of carburizing and quenching. "Our unique know-how regarding the temperature, duration, and other aspects of heat treatment built up through many years of experience is crucial to every step of the production process," says Mr. Kazunori Sasai of the company's Manufacturing Business Department.

Japanese people have loved pachinko as an easy-to-enjoy amusement for more than eighty years. The technology sealed into the tiny balls, only 11 millimeters in diameter, is still shining as brightly as ever.


Pachinko balls being quenched, and forming red strings as they fall into water.



Chromium plating line



Wire rods jointly developed with a steelmaker


A cross-section of a pachinko ball; the three-layered structure is visible


One of the reasons often cited for the survival of pachinko ball manufacturers in Osaka alone is that there are so many wire rod and drawn wire manufacturers in the Kansai region. Other relevant factors are that Higashi-Osaka City—a major center of metal processing—is one of the biggest production bases of bolts and nuts, common tertiary products made from wire rods, and that Sakai City has fostered the tradition of forging cutlery since the Muromachi period (1336–1573). Various kinds of steelmaking technology developed in Osaka are crystallized in pachinko balls, weighing a little over 5 grams each.

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