PRECISELY because the clock did not start as a practical tool shaped for a single purpose, it was destined to be the mother of machines. The clock broke down the walls between kinds of knowledge, ingenuity, and skill, and clockmakers were the first consciously to apply the theories of mechanics and physics to the making of machines. Progress came from the collaboration of scientists—Galileo [Galilei], [Christiaan] Huygens, [Robert] Hooke, and others—with craftsmen and mechanics.
Since clocks were the first modern measuring machines, clockmakers became the pioneer scientific-instrument makers. The enduring legacy of the pioneer clockmakers, though nothing could have been further from their minds, was the basic technology of machine tools. The two prime examples are the gear (or toothed wheel) and the screw. The introduction of the pendulum, by Galileo and then by Huygens, made it possible for clocks to be ten times more accurate than they had been, but this could be accomplished only by precisely divided and precisely cut toothed wheels. Clockmakers developed new, simpler, more precise techniques both for dividing the circumference of a circular metal plate into equal units and for cutting the gear teeth with an efficient profile. Clocks also required precision screws, which in turn required the improvement of the metal lathe.
Gears were, of course, the essential connective tissue in a mechanical clock. The teeth in the wheels within the clock were not apt to be accurately spaced or cleanly cut if they were hand-hewn. The first gear-cutting machine of which we have any record is the work of an Italian craftsman, Juanelo Torriano of Cremona (1501-1575), who went to Spain in 1540 to make an elegant large planetary clock for Emperor Charles V. Torriano spent twenty years planning a timepiece with eighteen hundred gear wheels and then three and a half years building it. “So every day (not counting holidays),” his friend reported, “he had to make…more than three wheels that were different in size, number and shape of teeth, and in the way in which they are placed and engaged. But in spite of the fact that this speed is miraculous, even more astounding is a most ingenious lathe that he invented…to carve out with a file iron wheels to the required dimension and uniformity of the teeth…no wheel was made twice because it always came out right the first time.” During Torriano’s lifetime his “lathe” was already being used by other clockmakers. It appears to have become the model for the “wheel-cutting engines” used by English and French clockmakers in the seventeenth century, when timepieces were reaching a wider market. Without such a device it would have been impossible for clocks to be made in large numbers for the commercial market. With such a gear-cutting machine, it was possible to make countless other machines and scientific instruments.
— Daniel J. Boorstin in The Discoverers: A history of man’s search to know his world and himself, (New York: Random House, February 1985), p. 64. First published (New York: Random House, 1983).
"Precisely because the clock did not start as a practical tool shaped for a single purpose"