William Oughtred and others developed the slide rule in the 17th century based on the emerging work on logarithms by John Napier. Before the advent of the pocket calculator, it was the most commonly used calculation tool in science and engineering. The use of slide rules continued to grow through the 1950s and 1960s even as digital computing devices were being gradually introduced; but around 1974 the electronic scientific calculator made it largely obsolete and most suppliers left the business.

The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.

The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.

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 complexcalculations such as logarithms. Estimates are that Hemmi sold over 15 million slide rules. They marketed theirslide 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.

**Models :**No.'s 30, 32, 34R, 34RK, 50W, 2640, 40RK, 76, 66, 64, 70, 2634, 45, 2664, 130, 136, 80K, 86K and 2690

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.

**Instruction Manual for Hemmi and others Slide rule**

**Click links below, To Use this Sliderule, (Virtual sliderule) :**

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