While the variations are endless the basic principles remain the same for the majority of mechanical movements. Timekeeping is accomplished by attaching hands to a set of wheels called the motion works and causing them to turn at a precise and consistent speed.

The motion works are under the dial and driven by the gear train. The gear train is usually made up of 4 wheels.

The gear train is powered by the mainspring which is coiled up and inserted into the barrel.

The watch is wound manually by turning the stem and crown or from the self-wind mechanism.

THE SELF WINDING MECHANISM:

The self-winding mechanisms come in many designs. All use a weight, gravity, and the motion of the wearer's arm to wind the watch without having to turn the crown. Some weights-particularly on many older watches-did not rotate 360 degrees. On most newer models the oscillating weight does rotate 360 degrees. Because of gravity the oscillating weight is always turning to “point” to the ground.

Through a series of gears the motion of the weight turns the mainspring in the barrel to wind it up. Once the mainspring is fully wound it will begin to slide around the inside of the barrel. This way even with excessive motion the watch never gets over wound.

Escapement

The speed of the wheels in the gear train is regulated by the escapement. The escapement consists of the escape wheel, the pallet fork, and the balance wheel. The escape wheel has teeth cut at precise angles to fit with the jewels of the pallet fork. The pallet fork pivots back and forth allowing one tooth at a time to pass. The speed of this action is regulated by the balance wheel and this is where the time keeping comes from.

It works like this. When there is no power on the mainspring the pallet fork rests in the center of two adjustable pins or this picture a non adjustable bridge . The pins or bridge determine how far the pallet can pivot from side to side. The teeth of the escape wheel then are resting near the angled portion of the pallet jewels called the impulse plane. When the watch is wound the wheels start to turn. A tooth from the escape wheel pushes on that angled impulse plane of the pallet jewel. This causes the pallet to swing to one side.

As the pallet swings from this push the tooth slides off the end of the jewel. As the wheel rotates another tooth hits the other pallet jewel on its straight side called the locking plane The combination of the angle of the tooth and the angle of the pallet jewel lock the pallet to one side. It would stay there if it were not for the balance wheel.

As the pallet has pivoted from the push of the escape wheel the other end called the fork knocks against a jewel-called the roller jewel- on the bottom of the balance wheel causing the balance wheel to rotate.

The balance wheel has a coiled spring attached to it called the hairspring. Once it receives the knock

or impulse from the pallet fork instead of traveling in a 360 degree rotation it only gets about 300 degrees before the hairspring pulls it back around toward its starting position. Because of its

momentum it travels past the starting position. When it does the roller jewel enters the fork causing the pallet to pivot and unlock from the escape wheel tooth. As it unlocks the tooth once again slides and pushes against the impulse surface of the pallet jewel. When the jewel receives this force from the escape wheel the pallet continues to pivot and picks up speed and before the balance wheel can rotate out of the way the fork hits the roller jewel sending it 300 degrees in the other direction and starts the whole process over again.

The full process of locking, unlocking, oscillating and other actions not previously mentioned takes place 8 times every second or 28,800 times per hour on most modern watches. This process creates 5 distinct sounds that happen so fast the the human ear only hears these combined into the single tick tick tick.

The watch's time keeping is regulated by the hairspring or the weight of the balance wheel depending on the design. Hairspring regulation is accomplished by the use of regulator. Moving the regulator pins up or down the length of the spring changes the amount of the spring that can vibrate. A shorter amount will vibrate faster and cause the watch to run faster.

All weights have to be adjusted exactly the same on both sides.

These are the basics of how a mechanical watch works.