Pinion wire. Horologists' term for steel wire ribbed in the shape of a pinion. See Plate [X, key A, Figure 51, 2], showing a section of seven-leaf pinion wire . Before a method was found for making this wire , they were forced to cut their pinions themselves. The procedure is inherently simple, but it is very difficult to achieve the precision required in making all the leaves perfectly uniform, as well as the slots between them. Therefore it took much of their time, and often they did not achieve all the requisite precision. By means of this wire , when it is well made, they are freed from all that difficulty, and making a pinion is simply filing between the leaves to give them the suitable shape and thickness. The invention of pinion wire and the wheel-cutting engine has rendered a great service to the practice of horology, expediting and greatly improving the making of those two essential parts of a watch, the wheels and the pinions.

The English were the first to make this wire ; the Genevans attempted to imitate them, but with little success, as their wire is still very imperfect, therefore horologists obtain almost all of it from England. Several have attempted to make it in this country, but unsuccessfully. M. Fournier, a maker of springs, also made an attempt, with no more success. Finally, M. Blackey, a skilled maker of springs, succeeded in making as fine a wire as the English; he may even be said to have surpassed them, because he makes very heavy wire for clocks, while they do not. In 1744 the Académie Royale des Sciences granted a very favorable certificate to his machine, and consequently he obtained an exclusive privilege for making this wire , for 15 years.