A mechanical watch is a clock that uses a clockwork mechanism to measure the passage of time, as opposed to a quartz clock, which functions electronically through a small battery, or a radio watch, which is a quartz clock synchronized with an atomic clock through radio waves. Mechanical watches are driven by a winding spring that must be wound periodically by hand or by a self-winding mechanism. Its force is transmitted through a series of gears, driving a balancer, a weighted wheel that oscillates back and forth at a constant speed. A device called the escapement releases the wheels of the watch to move forward a short distance with each swing of the balance wheel, moving the hands of the watch forward at a constant rate. The escapement is what makes the ticking sound heard in a working mechanical watch. Mechanical clocks evolved in Europe in the 17th century from the spring-operated clocks of the 15th century.

Mechanical clocks are usually not as accurate as quartz clocks, and they require periodic cleaning and calibration by a qualified watchmaker. Since the 1970s, quartz watches have taken over much of the watchmaking market, and mechanical watches are now mostly a high-end product, purchased for their aesthetic and luxury values, to appreciate their fine craftsmanship, or as a status symbol .

The internal mechanism of a watch, except for the dial and hands, is called the movement . All mechanical watches consist of five parts:

Additional functions on watches other than the main ones are traditionally called complications . Mechanical watches can have the following complications :

Mechanical watches are a mature technology , and most conventional watch movements have the same parts and work the same way.

The driving force , that powers the clock , a spiral band of spring steel , inside a cylindrical barrel , with the outer end of the spring , attached to the barrel . The force of the combat spring rotates the barrel. The barrel has gear teeth around the outside that turn the central wheel once an hour – this wheel has a shaft that runs through the dial. The sides in the cannon gear are attached to the dial with a friction fit ( which allows it to slide when the hand is set) and the minute hand is attached to the cannon gear. The cannon pinion drives a small 12: 1 reduction gear, called a movement work, which turns the hour wheel and hand once for every 12 revolutions of the minute hand.