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Before factories, watch parts were made and fitted by hand; a replacement often had to be made to fit one specific watch. Interchangeability required precise machine tools and gauges.
The American Waltham enterprise, begun in the early 1850s by Aaron Dennison and partners, is the classic example of adapting machine methods to watches. Other American firms, including Elgin, Hamilton and Illinois, followed.
Swiss firms responded after the 1876 Philadelphia exhibition, where reports such as Jacques David's highlighted the American lead. Mechanisation spread through ébauche making and manufactures.
Factory records became possible. Many American companies kept serial-number registers by grade and model, which is why their watches can often be researched more precisely than hand-made work.
Machine production did not end hand finishing: high grades still received adjustment, decoration and timing by skilled workers.
For repair, interchangeability means a correct factory part may exist, but grade, model and size must match; 'fits' does not mean original. Record substitutions when work is done.
Mass production also changed what a watch cost and who owned one. Inexpensive pin-lever and 'dollar' watches made by firms such as Waterbury, Ingersoll and later Westclox put timekeeping within reach of many households, using simplified construction rather than jewelled lever movements.
The change was uneven across countries. English trade structure adapted slowly; Swiss producers combined machine-made ébauches with established finishing networks; Japanese and later Soviet industries built factories in the twentieth century. Each tradition left different kinds of records for researchers.
Machine production made model and grade the key units of identification. When a factory movement is researched, the serial number is the route into those records; the dial name or case alone may be misleading, since cases were often sold separately in the United States.
The American system of manufacture
The American system of manufacturing emerged from armory practices, which utilized precise machine tools and quality control gauges to ensure uniform dimensions for identical parts. This approach, pioneered in the 1830s and 1840s by figures like Aaron Lufkin Dennison, aimed to minimize reliance on expert watchmakers for every assembly step by enabling lesser-skilled workers to perform final construction. Despite these advancements, the transition proved difficult because watch movements required much tighter tolerances than those found in products like firearms or sewing machines. Even by the early twentieth century, labor costs remained a significant challenge, accounting for the vast majority of production expenses for firms like the Elgin National Watch Company.
Manufacturers often developed their own specialized machinery, such as jigs and measuring devices, to achieve these strict production requirements. To reduce material waste, factories implemented statistical classification methods where parts were graded by size. Components that failed to meet the highest design specifications were not discarded but were instead systematically paired with other appropriately sized parts for use in lower-grade watch movements.
Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.