Simanaitis Says

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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.

Sir Joseph Whitworth, 1st Baronet, Bt FRS FRSA, 1803–1887, English engineer, entrepreneur, inventor, and philanthropist.

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. 

Above, best workshop practice (though not universal), Below, the Whitworth standard. Image from Wikipedia.

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.

British shipping in Balaclava Harbour, near Sevastopol, Crimea. Image from Dawlish Chronicles..

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.

The 1908 Brooklands Cadillac Model K trio. This and following image from GM Archives

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.

A jumble of Model K parts.

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. 

Image from Samstag Sales.

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 


  1. Paul Everett
    August 6, 2021

    You may have mentioned this already, but a favorite book on the subject is Witold Rybczynski’s “One Good Turn: A Natural History of the Screwdriver and the Screw.” I never knew there was so much going in when I torqued down that bolt.

  2. Valter Prieto Jr
    August 6, 2021

    Metric, or International System, is the only one which makes sense.

    • simanaitissays
      August 6, 2021

      Yep. That’s what 13-mm wrenches are for: all those 1/2-in jobs. (Though I’m also reminded of the dear old lady who objected to km/h as being too speedy.)

  3. Keith Jackson
    August 6, 2021

    As I see it, 13mm is a sloppy 1/2 inch, 19mm is a tight 3/4, There’s no real substitute for the right size. I’ve yet to find an adjustable spanner that doesn’t slip (I’m almost 74, so have been screwing around for a while).

    As for screwdrivers, as a Canadian I favour the Robertson and curse the two Henrys, Phillips and Ford, every time I open one of those hardware bags at the bottom of the carton.

    • simanaitissays
      August 6, 2021

      I’m reminded of a story from those with military background. From the start of training, it’s stressed “sockets first, box wrenches second, then and only then open-end wrenches, and never an adjustable.” At the end of the training, each is given a set of various sized adjustables.

  4. sabresoftware
    August 7, 2021

    And then there is the topic of screw driver types, including the original slot type, the Phillips (cross), the Canadian Robertson (square) and the Allen key (hex).

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