ProtractorsEngineering & Drafting
By the end of the 18th century, protractors were routinely manufactured by machinery, with the invention of dividing engines, such as Jesse Ramsden's, particularly important for enabling the precise division of a circle into fractions of angles. Makers produced protractors that read minute fractions of angles, particularly when a vernier was added to the instrument.
Mechanics or machinists also used protractors to draw designs for new types of machinery. For instance, there were several forms of limb protractors for draftsmen that both functioned as T-squares and provided angle measurement. Similarly, protractors assisted with the preparation of architectural drawings. The instruments were only displaced by the advent of computer-aided drafting in the late 20th century.
"Protractors - Engineering & Drafting" showing 1 items.
- In the late 19th century, American draftsmen experimented with different designs for making protractors more versatile. For instance, the secretive machinist Samuel Darling, who operated a separate partnership with Joseph R. Brown and Lucian Sharpe of Providence, R.I., between 1866 and 1892, patented a "bevel and protractor" on July 19, 1887. This was a nearly circular protractor with an extended arm that slid along and rotated around a ruler.
- Alton J. Shaw, who apprenticed in the main firm of Brown & Sharpe, came up with a design that was less cumbersome than Darling's. Although Shaw filed for a patent one month before Darling did, Shaw's patent was not granted until August 2, 1887. His protractor consisted of a circle with an extending arm, cut from sheet steel, which fit on a groove within a three-sided square, also cut from sheet steel. An advantage of this protractor was its reversibility. Shaw assigned his patent to Darling, Brown, & Sharpe on August 19 in exchange for $75. The firm marketed the protractor for $6.50, or for $7.75 with a case. In its catalogs, Brown & Sharpe adopted the British spelling, "draughtsmen's".
- This instrument is an example of Shaw's design. The protractor is divided by single degrees and marked by fives from 0 to 90 in the clockwise direction. Thirty more unnumbered divisions extend past the 90° mark. A vernier on the frame allows angles to be measured to one minute of arc. The interior of the protractor is marked: Darling, Brown & Sharpe. (/) Providence. R.I. (/) Pat. Aug. 2. 1887. The protractor is in a wood and morocco leather case that is lined with purple velvet. The case has broken apart into at least three pieces. A worn instruction sheet (ID number MA*336072.1.1), dated August 1889, is stored with the object. The instructions indicate that a guiding lever, which was placed in two of the eleven holes at the top of the protracting circle, is missing from the object.
- Shaw later moved to Milwaukee, Wis., and then to Muskegon, Mich., where he established the Shaw Electric Crane Company. The company became Lift-Tech International in 1986. The Brown & Sharpe Mfg. Co. absorbed Darling, Brown & Sharpe in 1892. After over a century as one of the largest American machining firms, Brown & Sharpe ceased manufacturing machine tools and drawing instruments in 1991. The firm now manufactures optical measuring instruments as a subsidiary of Hexagon Metrology.
- This protractor was owned by the renowned American designer of steam engines, Erasmus Darwin Leavitt Jr. (1836–1916), and donated by his granddaughter, Margaret van D. Rice.
- See also ID number 1990.0317.02.
- References: Oscar James Beale, Practical Treatise on Gearing (Providence, R.I.: Brown & Sharpe Mfg. Co., 1886), 73-75; Samuel Darling, "Bevel and Protractor" (U.S. Patent 366,651 issued July 19, 1887); Alton J. Shaw, "Protractor" (U.S. Patent 367,673 issued August 2, 1887); Amy Ackerberg-Hastings, "The Brown & Sharpe Draftsmen's Protractor," Rittenhouse 15, no. 1 (2001): 31–38; Henry Dexter Sharpe, A Measure of Perfection: The History of Brown & Sharpe (North Kingston, R.I.: Brown & Sharpe, 1949), http://www.roseantiquetools.com/id44.html.
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- Darling, Samuel
- Darling, Brown & Sharpe
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- Data Source
- National Museum of American History, Kenneth E. Behring Center