A simple mechanical watch contains about 130 components and more complex watches even contain hundreds of parts. The following glossary is here to help give you an idea about the basic components, their function, and to give you other watch terms that maybe helpful.

 The main parts of a simple mechanical watch include:

• Mainspring: provides power
• Balance Wheel: moves at a regular speed; functions with the Hairspring to mark the division of time
• Hairspring: oscillates; functions with the Balance Wheel to mark the division of time
• Escapement: distributes the impulses from the oscillator
• Gear Train: transmits power
• Winding Stem found in manually wound watches or Oscillating Weight in self-winding watches
• Dial Train: activates the hands

Glossary

A

Aperture: a small opening; in some watches, the dials have openings in which certain information is given such at the date or day of the week.

Applique: applied chapters; numerals or symbols cut out of a sheet of metal and fixed upon a dial.

Assembling: the process of fitting together the components of a movement. This used to be done entirely by hand but are now largely automated. However, a human watchmaker is crucial, especially for inspections and testing.

Assortiment: French term for the parts used to make an escapement.

Automatic Watch: a watch that has a mainspring that is wounds by the movementsof the owner's arm during wear. Invented by Abraham-Louis Perrelet of Switzerland in the 1700s, the automatic watch is based on the principle of terrestrial attraction, where a rotor turns and transmits its energy to the spring by means of an appropriate mechanism.

B

Balance: a moving part that is usually circular, moving on its axis of rotation. Coupled with the Hairspring, the Balance swings back and forth, dividing time into exact, equal parts. These back-and-forth movements of the balance are called "oscillations" and one oscillation is composed of two vibrations.

Bar (Lug): a thin metal rod fixed between the horns that attaches the wristband to the case.

Barrel: a thin cylindrical box containing the mainspring of the watch. The toothed rim of the barrel drives the train.

Bridge: part fixed to the main plate to form the frame of a watch movement. Other parts of the watch are mounted inside fo the frame, which is part of the ébauche.

C

Calibre: originally used to mean the size of a watch movement, this terms now refers to a type of movement, such as men's calibre or automatic calibre. When a calibre number is accompanied by the manufacturer's mark, it will also serve as an indication of origin.

Case: container that protects the watch-movement from water, dust, and shocks. 

Casing: process of inserting and fixing a movement into its case.

Chablon: French term for a watch movement where the components are not completely assembled.

Chronograph: a watch with two independent time systems; 1. indicates the time of day; 2. measures brief intervals of time. With a Chronograph, it is possible to measure the exact duration of a phenomenon but it is not to be confused with the chronometer, the stopwatch, or the timer.

Chronometer: a watch that has endured a series of precision tests in an official insitute. The requirements of the tests are very demanding.

Crown: knob located on the outside of a watch case and is used for winding the mainspring. For some watches, the crown can also be used to set calendar indications.

D

Date: number referring to a day of the month and is shown through an aperture. 

Dial: indicates the face or plate of material that bears the various markings to show the hours, minutes, and seconds. Dials can vary considerably in regards to shape, decoration, and material. The indications on a dial are given by means of numerals, divisions, or symbols or various types.

Direct-Drive: refers to a seconds-hand that moves forwards in a jarring movements.

Display: indicates time by either means of hands moving over a dial or by numerals appearing in one or more windows. These numerals may be completed by alphabetical indications or by signs of any other kind.

E

Ébauche: French term for a movement blank, such as a incomplete watch movement which is sold as a set of loose parts. The main plate, bridges, train, winding and setting mechanism, and the regulator make up the ébuche. However, the timing system, the escapement, and the mainspring are not considered parts of the ébuche.

Escapement: a set of parts that converts the rotary motion of the train into the back-and-forth motion.

Etablissage: French term for the method of manufacturing watches and/or movements by assemling their various components in the following operations: 1. inspection and stocking of the ébuche, 2. regulating the elements and other parts of the movement, 3. assembling, 4. springing and timing, 5. fitting the dial and hands, 6. casing, and 7. final inspection before packing and dispatching.

Etablisseur: French term for a watch factory that engages only in assembling watches by buying the components from suppliers.

F

Fly-back Hand: In a chronograph with analogue display, the additional second hand can remain superposed on the other one as it moves and can be stopped independently so that it can then be made to "fly back" to catch up with the other hand. It can also be stopped and reset to zero witht he other hand. 

H

Hand: indicator. Usually made of a thin, light piece of metal that is variable in form that moves over a graduated dial or scale. Most of the time, watches have three hands showing the hours, minutes, and seconds.

J

Jewel: bearing; end stone or pallet used for reducing friction. Jewels are generally made of synthetic material, except for precious or semi-precious stones that used in "de luxe" watches.

M

Main Plate: base plate where the rest of the watch movement is mounted.

Mainspring: the driving spring of a watch or clock and is contained in the barrel.

Marine Chronometer: the highly accurate mechanical or electronic timekeeper enclosed in a box and is used for determining the longitude on board a ship.

Middle: the middle part of the watch case where the movement is fitted.

Movement: assembly consisting of the principal elements and mechanisms of a watch or clock, such as the winding and setting mechanism, the mainspring, the train, the escapement, and the regulating elements. The movement consists of the ébuche as well.

R

Regulating Elements: set of parts that makes up the regulating system and the escapement. 

Repeater: a watch the strikes the hours by means of a mechanism operated by a bold or push-piece. There are various types of repeaters including the quarter-repeater, five-minute repeater, and minute repeater.

Rotor: a half-disc of heavy metal that is made to rotate inside the case of an automatic watch by the energy produced by the movement that is created while worn on the wrist. Its rotations continually wind the mainspring of the watch.

S

Second: a basic unit of time 

Set: setting of time; the process of bringing th ehands of a watch or clock to the position that corresponds to the exact time.

Shock Absorber: a resilient bearing that is intended to take up the shocks received by the balance staff and therefore protects its delicate pivots from damage.

Skeleton: where the case or other various parts of the watch are of transparent material.

Striking-Mechanism: automatic or hand-operated mechanism that strikes the hours, minutes, and so on.

T

Tachometer: instrument to measure speed; in watchmaking, it is a timer or chronograph with a graduated dial on which speed can be read off in another unit of time, such as kilometers.

Terminage: French term denoting the process of assembling watch parts for the account of a producer.

Termineur: French term for an independent watchmaker or workshop that assembles watches for a manufacturer.

Tourbillon: device invented to eliminate errors of rate in the vertical positions that consists of a mobile carriage or cage carrying all the parts of the escapement with the balance in the center. The escape pinion turns around the fixed fourth wheel and the case makes one revolution per minute, which nullifies errors of rate in the vertical positions.

V

Vibration: movement of a pendulum or other rotating movement that is limited by two consecutive positions. The balance of a mechanical watch makes about five or six vibrations per second but ones of high frequency may make up to 10 vibrations per second.

W

Watch Material: components for either producing watches or for repairing them.

Water Resistant: something made to prevent water from entering and damaging the watch. 

Winding: operation consisting in the tightening of the mainspring of a watch. Winding can either occur manually by rotating the crown or automatically during the movements of a swinging arm while an owner wears their watch.