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About Slide Rules

Our slide rule is a scientific instrument that makes possible easy calculation of multiplication and division, but also proportionality, square, cube and trigonometric functions by using a characteristic of logarithms, that is when a x b = c, log a + log b = log c (with a and b as positive numbers). This slide rule can also be used to calculate complex numbers and vectors, and combined with D1 rule, sin calculations are possible. Furthermore, by adding engineering and hydraulics specialty scales, calculations including stadia survey, curve installation and Manning formula are made possible.

20,000 hours of work were necessary to develop our slide rule. As bamboo tends to expand and contract with variations in humidity, our materials are heat-treated with care and we pay attention to wait at least one year and a half before completing a product to ensure scale accuracy and sliding smoothness. All these measures are taken in order to extend the life of our slide rules.
Hisashi Okura (1892 - 1960) Jiro Hemmi (1878 - 1953)
Hisashi Okura, the founder of Hemmi Slide Rule Co., Ltd. was born in Kumamoto prefecture, in the south of Japan.
Born in the Otsuka family, a family with a member in the government Cabinet during the Meiji era, he married the oldest daughter of the Okura family, owner of the then Okura brewing company (now Gekkeikan Sake) and became member of the family.
He assisted Jiro Hemmi in managing his shop and promoted actively exportation to respond to demand from foreign countries. He directed the development of slide rules which could compete with the well-known ones from other countries. He also implemented a research department in which he committed to developing original Japanese slide rules.
Jiro Hemmi is the father of Hemmi slide rules.
He was born in Tokyo and at the age of 13 he became artisan in Nakamura measuring instrument workshop where he started making scales.
He got passionate about his work, and when he was asked to make copies of a Mannheim slide rule, he was already the best scale maker of his time in Japan.
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