Machinery's Handbook, 31st Edition
2834
SI Metric Units Table 5. Units Outside SI, Accepted for Use with SI
Table 6. SI Prefixes
Standard of Length and the US Customary Unit System Among all units of measure, the history of standard of length traces a clear path from the less scientific approach of physical object standards used in past centuries to the today’s precise standards, based on physical constants on an atomic level. The primary Imperial yard was set by the British Weights and Measures Act of 1824. But it was partially destroyed in a fire in 1834, and replaced by a new standard, made of an alloy of copper, tin, and zinc. Between 1845 and 1855, forty copies of the Imperial yard were cast. Bronze yard No. 11 went to the United States, an exact copy of the British Imperial yard, in both form and material. By an Act of Congress, in 1866, the US legally recognized the meter as a standard of length equal to 39/39.37 = 0.9144 yard; for commercial purposes, 1 meter = 39.37 inches.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online