# PINION

, in Mechanics, is an arbor, or spindle, in the body of which are several notches, which are catched by the teeth of a wheel that serves to turn it round. Or a Pinion is any lesser wheel that plays in the teeth of a larger.

In a watch, &c, the notches of a Pinion are called leaves, and not teeth, as in other wheels; and their number is commonly 4, 5, 6, 8, &c.

Pinion of Report, is that Pinion, in a watch, commonly sixed on the arbor of a great wheel: and which used to have but four leaves in old watches; it drives the dial-wheel, and carries about the hand.

The number of turns to be laid upon the Pinion of report, is found by this proportion: as the beats in one turn of the great wheel, are to the beats in an h<*>ur, so are the hours on the face of the clock (viz 12 or 24), to the quotient of the hour-wheel or dial-wheel divided by the Pinion of report, that is, by the number of turns which the Pinion of report hath in one turn of the dialwheel. Which in numbers is . —Or thus; as the hours of the watch's going, are to the numbers of the turns of the fusee, so are the hours of the face, to the quotient of the Pinion of report. So, if the hours be 12, then as ; but if 24, then as .

This rule may serve to lay the Pinion of report on any other wheel, thus: as the beats in one turn of any wheel, are to the beats in an hour, so are the hours of the face, or dial-plate, of the watch, to the quotient of the dial-wheel divided by the Pinion of report, fixed on the spindle of the aforesaid wheel.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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