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At the Turn of a Screw: William Sellers, the Franklin Institute, and a Standard American Thread

1969; Johns Hopkins University Press; Volume: 10; Issue: 1 Linguagem: Inglês

10.1353/tech.1969.a892312

1097-3729

Bruce Sinclair,

Metallurgy and Cultural Artifacts

At the Turn of a Screw: William Sellers, the Franklin Institute, and a Standard American Thread BRUCE SINCLAIR At a time when the superb drama of exploiting a new continent filled the minds of most Americans, nineteenth-century technical arguments about the shape and number of threads on a screw often have a remote, somewhat comic quality—a bit like Jonathan Swift’s mock epic struggle between the Little Enders and the Big Enders. But the issue was not a matter of satirical trivia. Industrial development on a national scale demanded that nuts and bolts of the same diameter be interchangeable. Interchangeability, in turn, required that manufacturers conform to a standard system which fixed the contour of screw threads and estab­ lished for each diameter the number of threads per inch. For America, in 1860, no such standard existed. Since that era also marked the emer­ gence of this country into the arena of international industrial competi­ tion, the search for a standard cast reflections which illuminate such related considerations as a national style of engineering, American in­ dustrial practice, and the role of government in technological change. The most prevalent system—where system was used at all—was that which had first been proposed in 1841 by England’s Sir Joseph Whit­ worth.1 Whitworth’s standard was a synthesis of the best English prac­ tice and answered the general case well enough so that it was widely em­ ployed. American usage was disuniform, however, varying from manu­ facturer to manufacturer and from locality to locality. Some firms devel­ oped systems to fit the particular requirements of their own processes. Others purposely used special threads to prevent outside repairs on their own machinery, in the same vein as the Erie Railroad’s ill-fated use of wide-gauge track. By the 1860’s, the appalling lack of national uniform­ ity clearly called for reform. “If there is any one thing in the transacDr . Sinclair, of Kansas State University, is the author of Early Research at the Franklin Institute: The Investigation into the Causes of Steam Boiler Explosions, 1830-1831. 1 Sir Joseph Whitworth, “On a Uniform System of Screw Threads,” Papers on Mechanical Subjects (London, 1885), pp. 17-26. 20 21 At the Turn of a Screw tions of the machine shop more incomprehensible than another,” the editor of Scientific American claimed in 1863, “it is the want of some settled size or number for screw threads.”2 To eliminate the anarchy, the magazine called for some agreement among the country’s principal manufacturers or, failing that, governmental action. Whatever the stand­ ard, Whitworth or any other, the adoption of some uniform national system of screw threads was of vital necessity. But the development of a standard in the first instance posed certain difficulties. As Whitworth had pointed out, a system depended on com­ promise, not on theory or experimentation.3 There was simply no way in which all the factors involved in screw-thread design could be stated as a precise rule, applicable to all cases. Where principle provided no final answer, practice determined the issue. That opened the door to non-technical factors. A further difficulty in America was that no single agency seemed capable of dealing with the problem. Editorial injunc­ tions notwithstanding, the federal government had no ready means either to develop a system or to regulate its usage, not even to speak of an inclination to do so. Nor did any professional engineering society exist to propose a standard and advance its adoption. It was in this appar­ ent vacuum that William Sellers presented a paper before a meeting of the Franklin Institute at Philadelphia in April 1864 outlining a uniform system for American screw threads. In his paper, Sellers addressed himself immediately to the central ques­ tion: Why should there be yet another system of threads? Why should not Americans adopt the Whitworth standard and by its consistent usage rationalize current practice? The English system was the result of sev­ eral years of study by an outstanding mechanician, who had carefully analyzed the three main factors of screw-thread design—pitch, or the number of threads per inch, thread depth, and thread form...