What Are the Parts Inside a Watch?

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Horology, the art of measuring time, is a centuries old practice long associated with the making of timepieces such as watches. The complex inner workings of a watch are the result of more than 100 different parts. The combination of precise mechanical pieces and transferable energy are what make every type of watch--from the cheapest wind up to luxury timepieces--work.

Mainspring

The mainspring is the source behind the motive power of a watch. Motive power is needed to make the watch hands turn, effectively enabling it to tell time. The mainspring is little more than a small, thin spring turned by rotating the crown on the side of the watch face. The motive power comes from the turn of the crown. This is the part of the watch that protrudes from the side of the watch bezel and allows the wearers to set the watch hands to the correct time. This rotation of the crown transfers the movement and energy into the mainspring. From there the energy is stored inside the mainspring where it is utilized to work the mechanisms of the watch. The mainspring is usually constructed from hardened steel.

Balance Wheel

The balance wheel is what enables the watch to keep time. Weighted, the balance wheel rotates back and forth and allows the gears in the watch to advance with each rotation. This in turn moves the watch hands a set amount. Balance wheels are usually made from a metal alloy that is part iron and part copper. A balance wheel is not only used in watches, but also in clocks, kitchen timers and even vaults. It is an essential part of time keeping machinery. Balance wheels vary in precision, depending on the skills of the watch maker and the quality of the manufacturer. Needless to say, the more expensive the watch, the more likely it is to have an accurate balance wheel. Although many of today's watches are battery powered, balance wheels are still used in self-powered time pieces such as kinetic watches.

Gear Train

A gear train is needed to transfer the energy from the mainspring to the balance wheel. The gear train increases the speed of the mainspring rotation, enabling it to operate on the energy it has stored. It also operates many other parts of the watch. By transferring the energy to the balance wheel, the gear train activates other wheels that oversee the revolutions of the seconds, minutes and hours. The gear train is only needed in analog watches, not in contemporary digital watches. Digital watches are battery powered and the time displays on an LCD screen.