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Keuffel & Esser 4012 Thacher Cylindrical Slide Rule

Keuffel & Esser 4012 Thacher Cylindrical Slide Rule

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The brass core of this cylindrical slide rule is covered by paper marked with forty A scales. The core fits in an open rotating frame that holds twenty metal slats; each slat is lined with cloth, covered with paper, and marked with two B and two C scales. Wooden knobs on each end of the core rotate the instrument. The frame is attached to a mahogany base.
The first A scale runs from 100 to 112 and the fortieth runs from 946 to 100 to 105. The first B scale runs from 100 to 112, the last from 946 to 100 to 105. The first C scale runs from 100 to 334, the last from 308 to 305. The paper covering the core is also printed in italics on the right side: Made by Keuffel & Esser Co., New York; Patented by Edwin Thatcher [sic], C.E. Nov. 1st., 1881.
The paper of instructions and rules for operating THACHER'S CALCULATING INSTRUMENT, normally glued to the top front of the base, is coming loose and is torn on this example. A large chip is also missing from the left handle. The top back of the base is stamped: KEUFFEL & ESSER CO. (encircling N.Y.); 4012 (/) 4218; TRADEMARK (below the K&E logo of a lion).
Keuffel & Esser sold versions of the Thacher cylindrical slide rule from about 1883 until about 1950. There were two models, one with a magnifying glass (K&E model 1741 before 1900, K&E model 4013 after) and one without (K&E model 1740 before 1900, K&E model 4012 after). This is a model 4012; the serial number suggests it was manufactured around 1915. The marking on the core also no longer references W. F. Stanley, the English firm that originally manufactured the instrument for sale by K&E. Stanley continued to provide the engine-divided scales after K&E began making the rest of the instrument in 1887. K&E took over printing the scales in the 1910s. Model 4012 sold for $35.00 in 1916, $60.00 in 1922, and $70.00 in 1927.
Compare markings on the core to MA.322730. See also MA.312866 and MA.326628.
References: Wayne E. Feely, "Thacher Cylindrical Slide Rules," The Chronicle of the Early American Industries Association 50 (1997): 125–127; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1916), 22; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1922), 21; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1927), 20.
Currently not on view
Object Name
calculating rule
slide rule
date made
ca 1915
Keuffel & Esser Co.
place made
United States: New York, New York City
Physical Description
wood (part material)
cloth (part material)
brass (part material)
paper (overall material)
overall: 14 cm x 57.5 cm x 14.3 cm; 5 1/2 in x 22 5/8 in x 5 5/8 in
ID Number
accession number
maker number
catalog number
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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During the summer of 1964 I attended a National Science Foundation Math seminar for several weeks on the campus of Northern Michigan University in Marquette, MI. One of these calculators was on a table in the back of one of our classrooms. I took an interest in the calculator and wrote to K & E, along with sending them a photo. I received a fine type written letter from J.M. Cowles, Sales Service at K&E.. Cowles wrote that they began recording serial numbers in the 1920's and that the serial # of 1668 on the NMU calculator indicated a very old calculator. Cowles also wrote that they maintained repair facilities for Thacher calculators and that many calculators were still in use at that time in steel mills and steel fabricating plants. I was told by someone at NMU that railway engineers used these calculators in the design of track layouts and grades. I still have a black & white snapshot of the calculators, its wooden case, users manual. I hope NMU still has this museum piece. The following year I learned a lot about slide rules in my freshman year at Michigan Tech, but I never forgot the elegance of the Thatcher calculator.
My family donated an early model used by my Grandfather (Dean of Engineering @ U of Wyoming) and Uncle (Boeing Engineer) to the Engineering School at Colorado State University. They were floored w/ the opportunity to have one to have it for their archives. It came complete w/ magnifying glass and Manual. Last time I went to observe it there was an Engineering History Professor researching water rights/engineering topics from Nebraska-Kearney who had never seen a Thatcher. He was like a kid in a candy store.
I have one of these complete with original manual and beautiful box-jointed wooden case. My wife received it from National Life Insurance Co. where she worked in 1950, where they were still in occasional use when they did not have enough mechanical calculators. I used it to check the accuracy of student papers while teaching trigonometry in freshman college classes. (The students had to use 5-place log tables!) It is a beautifully built old machine first put on the market around 1884, mine was sold about 1932.. The great majority of you who read this (that's around 2 out of the three of you) cannot imagine the magnitude of the changes in computing that has occurred in my lifetime. Pencil and paper to slide rules (6 inches to 50 feet in length); to mechanical to electrical to electronic adding machines; to vacuum tube to discrete transistor to lo-res integration to hi-res integration computers; from massive building filling computers to faster, increased power on a desk-top and in the pocket., I have seen and used it all and I am still blown away at the unbelievable quantity data available on internet. I hope all you kids appreciate it (That's anybody 60 years old and under.)

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