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NOW THAT I have your attention, let’s talk about the historical standardization of fasteners: nuts, bolts, and screws. Today’s tidbits include a gunboat rush order, a Cadillac exhibition, and which wrench do I need anyway.
Options Galore. The simple screw fastener has scads of geometric specs: its length, diameter(s), thread pitch, angle, and depth. And, if a nut/bolt combination, the nut and bolt diameters and shape have to be considered.
Back when such hardware was hand-made, these decisions were the choices of individual artisans. Interchangeability didn’t become an issue until around 1800 and the invention of the screw-cutting lathe.
Joseph Whitworth’s Specs. In 1841, English engineer Joseph Whitworth devised the world’s first national screw thread standard, what evolved into the BSW, British Standard Whitworth system. It specified a 55-degree thread angle, thread depth and radius each a specified proportion of pitch, and pitch increasing with diameter in defined steps.
The Crimean War. Wikipedia says that the Crimean War, October 1853–February 1856, was precipitated by a dispute between France promoting Roman Catholicism and Russia favoring the Eastern Orthodox Church. Ultimately, Russia battled France, the Ottoman Empire, the U.K., and Sardinia in what Wikipedia cites as “a war that stood out for its ‘notoriously incompetent international butchery.’ ”
Pause here to ponder the matter of history repeating itself, one way or another.
At the onset of the Crimean War, Admiral Sir Charles Napier demanded that 120 gunboats be built within 90 days. Engineer John Penn applied Whitworth standards to this manufacturing challenge.
Gunboat Interchangeability! Wikipedia notes that Penn “had a pair of engines on hand of the exact size. He took them to pieces and he distributed the parts among the best machine shops in the country, telling each to make ninety sets exactly in all respects to the sample. The orders were executed with unfailing regularity.”
Later, in the U.S.A. In 1905, the Society of Automobile Engineers was formed, with Henry Ford its first vice president. Renamed the Society of Automotive Engineers in 1917, more recently (2006) SAE International, the organization promoted standardization early on with a 1914 SAE Data Book defining screw thread sizes.
Cadillac’s Achievement. Henry Leland, one of Cadillac’s founders, was SAE president in 1912–1913. Even before this, as described in “Cadillac’s Dewar Trophy,” Leland’s 1908 Cadillac Model K was built with interchangeable parts.
Interchangeability earned Cadillac the 1908 Dewar Trophy. Its London agent selected three Model Ks from stock, demonstrated them at the Brooklands Circuit, then completely disassembled them. Royal Automobile Club officials then scrambled everything into a pile of 2163 pieces and swapped 89 of these with replacements selected from the agent’s supplies.
Three Model Ks were assembled from this. Each was fired up and lapped Brooklands for 500 miles. One of them went on to win the 1908 R.A.C. Reliability Run.
But Which Wrench? Even the rigors of two world wars didn’t standardize hardware among countries. By the 1950s, the Brits had British Standard Whitworth; much of Europe had metric, now termed Systeme International, SI; and the U.S. and Canada had Unified Thread Standard, UTS.
That is, 70 years ago, U.S. cars were built largely to UTS; MGs and Jaguars, to BSW; Renaults and Mercedes-Benz to metric.
It was more than which size wrench, however. A Whitworth wrench is sized according to the diameter of the bolt’s shank, not its head. Thus, for example, a 1/4 W Whitworth wrench is a bit larger than a 1/2-inch American wrench. Michael Grant’s article at Moss Motoring gives more details.
By the way, at the risk of mangling nuts, bolts, or both, a 13-mm metric fits a satisfying number of applications. So does a 19-mm. So does an adjustable. ds
© Dennis Simanaitis, SimanaitisSays, 2021