Protractors - Engineering & 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 12 items.
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Brown & Sharpe 510 Draftsman's Protractor
- Description
- See also ID number 1977.0460.01. After the inventor of this draftsman's protractor, Alton J. Shaw, left Darling, Brown & Sharpe of Providence, R.I., Samuel Darling patented a vernier scale that was a fraction of the size of a standard vernier scale. Darling then claimed to apply his vernier to the draftsman's protractor, replacing the original patent date in the maker's mark with the December 2, 1890, date of this patent. See, for example, the illustration in Brown & Sharpe's 1899 Catalogue No. 101 and Price Lists. This vernier read to only five minutes of accuracy, while Shaw's earlier vernier read to one minute of accuracy. Darling argued, however, that the coarser scale was easier to read and sufficed for most situations that arose in engineering drawing.
- In any event, the draftsman's protractor continued to sell steadily into the 20th century. Advertisements extolled the instrument's versatility, including its ability to function as a drawing triangle and as an extension of a T-square. The original patent date reappeared on the instrument in 1902 and 1904 but disappeared again by 1916, by which time Brown & Sharpe also changed the protractor's catalog number from 530 to 510. Other dealers, including Keuffel & Esser, W. & L. E. Gurley, and L. S. Starrett, also sold the draftsmen's protractor.
- The chief difference between this example of the instrument and ID number 1977.0460.01 is the reduced precision of the vernier, which is even marked: FIVE MINUTES. This protractor has 40 unmarked divisions, instead of 30. The signature is: 510; BROWN & SHARPE MFG. CO. (/) PROVIDENCE. R.I. U.S.A. The handle also bears the Brown & Sharpe logo of two rectangles at right angles to one another, with the letters B∙S above the horizontal rectangle and the words TRADE MARK below the horizontal rectangle. Of surviving 20th-century Brown & Sharpe catalogs, this protractor most closely resembles the illustration printed in 1925. The extending arm of the protractor is rusting.
- The protractor is stored in a blue paper box covered with the company logo and the words BROWN & SHARPE. A label on one end of the lid reads: 510; ORDER BY NUMBER 599-510 (/) BROWN & SHARPE DRAFTSMEN'S PROTRACTOR (/) MADE IN U.S.A. A label on the other end of the lid reads: POST (/) 0585 (/) THE FREDERICK POST CO. CHICAGO. Post retailed scientific and drawing instruments in the 20th century. An undated sheet with tables of angles for dividing circles and for tapers per foot is in the box.
- References: Samuel Darling, "Vernier-Scale" (U.S. Patent 442,020 issued December 2, 1890); Kenneth L. Cope, intro., A Brown & Sharpe Catalogue Collection, 1868 to 1899 (Mendham, N.J.: The Astragal Press, 1997); Brown & Sharpe Mfg. Co., Catalogue (Providence, R.I., 1902), 372; Brown & Sharpe Mfg. Co., Catalogue No. 138 (Providence, R.I., 1925), 504–505.
- Location
- Currently not on view
- date made
- ca 1925
- maker
- Brown and Sharpe Manufacturing Company
- ID Number
- 1990.0317.02
- accession number
- 1990.0317
- catalog number
- 1990.0317.02
- Data Source
- National Museum of American History, Kenneth E. Behring Center
Semicircular Protractor
- Description
- This semicircular brass protractor is divided by single degrees and marked by tens from 10° to 170° in both the clockwise and counterclockwise directions. The origin point is marked with an arrow. A 2-1/2 inch ruler, divided by sixteenths of an inch, runs along the lower edge of the protractor. The letters U.S.A. are engraved above the right end of the ruler. No maker's mark is present.
- Location
- Currently not on view
- date made
- ca 1930
- ID Number
- 1981.0933.19
- accession number
- 1981.0933
- catalog number
- 1981.0933.19
- Data Source
- National Museum of American History, Kenneth E. Behring Center