Directions for the Use of Hemmi Slide Rules

Directions for the Use of Hemmi Slide Rules

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Usage conditions apply
This stapled ten-page leaflet arrived with 1982.0386.02. It is marked "Printed in Japan" and probably dates to the mid-1930s. It is titled, Short Directions for the Use of the "Hemmi's" Bamboo Slide Rules, and there are indications throughout the text that its author was not a native speaker of English.
The leaflet explains what a slide rule is. There are sections for Hemmi Normal Slide Rules, the Electro Slide Rule with Log Log Scale, and the Improved Slide Rule. The leaflet also contains an illustration of reading graduations on the scales, an explanation of Hemmi's construction techniques, and various technical problems that could be solved with slide rules. ID number 1982.0386.02 resembles the slide rule illustrated on p. 1, although the drawing shows a ruler in inches on the top edge and depicts PATENT No 58115 as written on the indicator. The example in the collections lacks the ruler and the reference to what is presumably a Japanese patent.
Currently not on view
Object Name
date made
place made
Japan: Japan
Physical Description
paper (overall material)
overall: 26.5 cm x 19.4 cm; 10 7/16 in x 7 5/8 in
ID Number
accession number
catalog number
Credit Line
Gift of John A. Betcher
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History
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The 10 cm pocket rule is marked with a "C" on the C scale . The value is about 1.125. What is that mark for?
c=1.128 is square root of (4/Pi). it is used for converting between circle diameter 'd' and area 'a': 1. align 'c' with 'd' on D 2. set hairline to index on C 3. read area 'a' on hairline on A

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