Darling, Brown and Sharpe Triangular Scale for Draughtsmen

This nickel-plated steel instrument is crimped in the middle so that the scales along both edges are angled, giving the object the appearance of a triangle and bringing the scale closer to the draftsman's work. Both edges have scales dividing three inches into 96 parts and scales divided to 3" and numbered by ones from 0 to 3. One edge is marked: D.B.&S. PROV. R.I. Pt. Aug. 3. 80. The crimp is marked: No. 1.
Draftsmen and architects could use this rule to make scale drawings in which 3" = 1'. Samuel Darling, a machinist who partnered between 1866 and 1892 with Joseph R. Brown and Lucian Sharpe of Providence, R.I., patented the general design in 1880. He desired a material that was not as susceptible to environmental changes as wood and a design that was not as heavy and expensive as the early forms of tubular triangular rules being manufactured by Darling, Brown & Sharpe and other firms.
Darling, Brown & Sharpe sold the rule in graduations from 3" = 1' to 1/2" = 1' for $1.00. ID number 1977.0460.07 is the same rule with a 1" = 1' scale. For engineers, the rule was available divided from 20ths to 1,000ths of an inch. A "miscellaneous" version had different scales on each edge, graduated along the entire edge in increments from 1/16" to 1/100". In its advertisements, which used the English spelling for "draughtsmen," the company explained that putting only one scale on each instrument would help prevent draftsmen from becoming confused and making mistakes.
The Brown & Sharpe Manufacturing Company continued to sell the rule after Darling's interest was bought out in 1892. The company then offered the scale in graduations down to 1/8" = 1' and increased the price to $1.25. By 1929, Brown & Sharpe offered only the miscellaneous version for $2.00. This example 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.
References: Samuel Darling, "Graduated Measuring Rule" (U.S. Patent 230,619 issued August 3, 1880); Kenneth L. Cope, intro., A Brown & Sharpe Catalogue Collection, 1868 to 1899 (Mendham, N.J.: The Astragal Press, 1997), 119, 160–161; Brown & Sharpe Mfg. Co., Machinery and Tools, no. 136 (Providence, R.I., 1916), 537–539; Brown & Sharpe Mfg. Co., Small Tools Catalog No. 31 (Providence, R.I., 1929), 97; 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.
Currently not on view
Object Name
rule, triangular
scale rule
date made
Darling, Brown & Sharpe
Physical Description
steel (overall material)
nickel (overall material)
overall: 1.3 cm x 31.2 cm x 2.4 cm; 1/2 in x 12 9/32 in x 15/16 in
place made
United States: Rhode Island, Providence
ID Number
accession number
catalog number
Scale Rules
Science & Mathematics
Drafting, Engineering
See more items in
Medicine and Science: Mathematics
Scale Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Margaret van D. Rice
Additional Media

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