What is the primary purpose of a watch's balance?

The primary purpose of a watch's balance is to regulate the watch's movement. The balance wheel is a crucial component in the timekeeping mechanism of a mechanical watch, working in conjunction with the escape wheel and balance spring to control the release of energy from the mainspring. This regulation ensures that the gear train moves at a consistent rate, allowing the watch to maintain accurate time.

By oscillating back and forth at a precise frequency, the balance wheel helps divide time into equal units, which is essential for accurate timekeeping. In essence, the balance is vital for maintaining the regularity of the watch's movement, directly influencing its ability to keep time accurately. This fundamental role is what distinguishes watches designed for precision from those that are primarily ornamental.