tremendous technological advance, but later advancements would make screws even cheaper and more prevalent yet again. These began in the 1840s with the adaptation of the engine lathe with a turret-head toolholder to create the turret lathe. This development greatly reduced the time, effort, and skill needed from the machine operator to produce each machine screw. Single-pointing was forgone in favor of die head cutting for such medium- and high-volume repetitive production. Then, in the 1870s, the turret lathe's part-cutting cycle (sequence of movements) was automated by being put under cam control, in a way very similar to how music boxes and player pianos can play a tune automatically. According to Rolt (1965), the first person to develop such a machine was Christopher Miner Spencer, a New England inventor. Charles Vander Woerd may have contemporarily independently invented a machine similar to Spencer's. However, the wood-screw-making machines of the 1840s and 1850s [special-purpose factory production machine tools as opposed to small-machine-shop machine tools], such as those developed by Cullen Whipple of the New England Screw Company and Thomas J. Sloan of the American Screw Company, had anticipated the machines of Spencer and Vander Woerd in various ways, albeit approaching the problem of automated screw production from a different commercial angle. All of the above machine tools (i.e., screw-cutting lathes; suitably equipped engine lathes and bench lathes; turret lathes; turret-lathe-derived screw machines; and wood-screw-factory screw machines) were sometimes called "screw machines" during this era (logically enough, given that they were machines tailored to screw making). The nomenclatural evolution whereby the term "screw machine" is often used more narrowly than that is discussed above. Spencer patented his idea in 1873; but his patent failed to protect the cam drum, which Spencer called the 'brain wheel'. Therefore, many other people quickly took up the idea. Later important developers of fully automatic lathes included S. L. Worsley, who developed a single-spindle machine for Brown & Sharpe, Edwin C. Henn, Reinhold Hakewessel, and George O. Gridley, who developed multiple-spindle variants and who was involved with a succession of corporations (Acme, National, National-Acme, Windsor Machine Company, Acme-Gridley, New Britain-Gridley); Edward P. Bullard Jr, who led the development of the Bullard Mult-Au-Matic; F.C. Fay and Otto A. Schaum, who developed the Fay automatic lathe; Ralph Flanders and his brother Ernest, who further refined the Fay lathe and developed the automatic screw thread grinder. Meanwhile, engineers in Switzerland were