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Hemmi Slide Rules

Hemmi was a Japanese company that began making slide rules in 1895 and continued production until 1976. A mechanical analog computer, the slide rule was standard equipment for most high school students until the advent of the hand-held calculator. The slide rule was used for multiplication and division, but was also capable of more complex calculations such as logarithms. Estimates are that Hemmi sold over 15 million slide rules. They marketed their slide rule in the United States under the name Sun. They also made slide rules for Fredrik Post and Hughes-Owen/Geotec and the other company names imprinted on the Hemmi slide rule.

Uses
- Slide rules were a calculator that did everything except add and subtract. The scales varied, but could include trigonometry, logarithmic, natural log, pi, square and square root, reciprocal or any mathematical function a user needed.
Design
- Hemmi made several different models over the years. Most were duplex that had scales on both sides. They range in size from 4 inches to 20 inches long. Hemmi also made circular models. Sometimes, Hemmi sometimes copied other company’s popular slide rule models. Hemmi made special purpose models for electrical, civil, chemical and mechanical engineering. The chemical slide rules had scales such as atomic weights, temperature conversions, pressure and expansion scales instead of trigonometry scales. The electrical models had scales specific to electrical engineering calculations. One of the most popular models was the Post Versalog 1450 and Hughes Owens 1777. It was the same slide rule, but Hemmi gave it different numbers to distinguish the company. The Versalog was a 10-inch rule made by between 1951 and 1973. During that time, the Versalog 1450 was the most popular slide rule Hemmi made for the United States and Canada.
The Demise
- Hemmi slide rules went the way of all slide rules after 1973. They went into drawers and closets because of the Hewlett Packard HP-35 calculator. It replaced the slide rule because it did everything a slide rule could do. When more companies began making hand-held calculators, the price for them came down, and sealed the slide rule's fate. They soon became a nostalgic curiosity and a collector’s item.

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