History of Toyota. Part 16 (1921-1924): Introduction of the Metric System

Truck specifications converting inches to meters

In conjunction with the start of operations at the Koromo Plant, a switch was made from the imperial measurement system (inches and pounds) to the metric system (meters and grams).

The Revised Weights and Measures Law was promulgated on April 12, 1921 (went into effect July 1, 1924), and Japan adopted the metric system. At the time, however, the traditional Japanese system (which measured length in shaku and weight in kan) was in widespread use in daily life, and the imperial system, which had been introduced with British and American machinery, was commonly used in manufacturing industries.

When Toyoda Automatic Loom Works, Ltd. began manufacturing automobiles, workers came from many different fields, and they arbitrarily used the Japanese measurement system with which they were most familiar. At the plant, inches were used alongside sun, bu and other Japanese units of measurement were used, with 1 inch being referred to as 1 sun, one-eighth inch called 1 bu, and one-sixteenth inch called 5 rin. Therefore it was necessary to be very certain concerning measurements.

By switching measurement systems from imperial to metric, it became impossible to use earlier parts.1 At the same time, jigs, tools, and gauges were replaced, and it was necessary to re-create all drawings. This was a massive job that required considerable labor and expense, but Kiichiro said, "If the automotive industry continues using inches, the nation will suffer extreme loss... It would be inexcusable to the citizenry of the future if we did not adopt the metric system, no matter what the sacrifice".