Watch Glossary

Amplitude:
The swing of a balance. The maximum swing from its normal at rest position to its furthest distance from rest (usually about 300 degrees).

Antimagnetic:
Said of a watch if the normally magnetic parts of that mechanism are unaffected by a magnetic field. This is achieved by the use of non-magnetic metal alloys such as palladium alloys.

Antireflection, Antireflective:
A treatment on watch crystal to eliminate light reflection and improve legibility of the watch dial.

Arbor:
The spindle, shaft, or axle upon which the wheels of a watch train are mounted.

Automatic:
A watch whose mechanical movement is wound automatically, typically by the movement of the wearer. Also, known as a "self-winding" watch. In most automatics, a rotating weight, set into motion by moving the wrist, winds the spring barrel via the gear train of the watch movement.

Automation:
A watch with animated figures, placed on the dial or case, actuated by the going, striking, musical or repeating train.

Balance:
Together with the balance spring, the balance, often said to be the "heart" of the watch, is an oscillating little wheel, just a few millimeters in diameter, that swings to and fro and determines the frequency of the watch, and hence the timekeeping ability of the watch. As the balance works like a pendulum, the balance spring's function consists of its elastic return and starting of a new oscillation. This combined action determines the frequency (the number of vibrations per hour) and affects the rotation speed of the different wheels. The balance, by its oscillations, at every vibration (through the action of pallets), frees a tooth of the escape wheel. From this, motion is transmitted to the fourth wheel, which makes a revolution in one minute, to the third and then the center wheel, the latter making a full rotation in one hour.

Balance Screws:
Prior to the advent of the perfectly weighted balance by use of a smooth ring, balances were fitted with weighted screws to get the exact impetus desired.

Balance Spring:
Spiral spring together with the balance, determines the movement's precision. The sprung balance regulates the timekeeping, the period of each swing depending upon the ratio of the moment of inertia of the balance to the stiffness or elasticity of the spring. A. L. Breguet introduced a spiral spring with an overcoil raised and turned in towards the center, which ensures the concentric development of the spring as the balance oscillates. A self-compensating spring is one, which is made of an alloy impervious to temperature changes.

Balance Staff:
The spindle or arbor upon which the balance is mounted.

Bar:
A metal plate secured to the movement plate, leaving room for a gear wheel or pinion. The balance is usually stored in a bar called the balance cock.

Barrel:
A cylindrical barrel with a toothed rim that meshes with the first pinion of the watch train. The barrel contains the main spring that is wound around an arbor, turned by the winding crown, or in the case of automatic movements, by the gear powered by the rotor.

Beat:
The multiple sound of the escapement action heard as the "tick."

Beveling:
Grinding of edges of plates, bridges, or bars of a movement to give it a high polish. Beveling treatment is typically found in high-grade movements.

Bezel:
The top portion of a case, sometimes holding the crystal.

Bimetallic:
Formed of two different metals, usually brass and steel, whose different coefficients of expansion are used for compensating the effects of temperature changes on a steel balance spring.

Breguet Overcoil:
See Balance Spring

Bridge:
A metal plate fastened to the main plate by means of screws leaving room for a gear or pinion.

Caliber:
A term that refers to the size and type of watch movement.

Case:
Container housing and protecting the watch movement, typically made up of three parts: bezel, middle, and case back.

Center Wheel:
The wheel, centrally placed, the arbor of which carries the minute hand.

Champleve:
Hand treatment done on the dial or case surface by hollowing out an area of metal with a graver and subsequently filing the hollows with enamel.

Chronograph:
A watch that shows not only the time of day but includes a timer that can be started and stopped at will to time an event.

Chronometer:
A high precision watch that has passed a series of tests and obtained a running bulleting (e.g., one with a deviation of no more than five seconds a day for mechanical movements) and a certificate by an independent Swiss control official, such as the C.O.S.C.

Circular Graining:
Surface decoration applied to plates, bridges, and rotors comprising an even pattern of partially overlapping dots, applied with a quickly rotating plastic or wooden peg.

Cloisonne:
A type of enamel work, mainly used for the decoration of dials, in which the outlines of the drawing are formed by thin gold threads. Colored enamels then fill the hollowed out portions. After oven firing, the surface is smoothed until the gold threads reappear. The intricate crafting and tricky firing procedures raise this type of enameling to an art form all its own.

Cock:
A metal plate having one end fastened to the movement plate and the other end supporting the pivot of a wheel. The balance cock supports the top pivot of the balance staff and is mounted on the top plate of the watch movement.

Complication:
Additional function other than basic timekeeping of the hours, minutes, and seconds. Although taken for granted, certain features such as automatic winding or date are considered complications. The main complications are power reserve, moonphase, GMT, and full calendars. Great complications are split second chronographs, perpetual calendars, tourbillons, and minute repeaters.

C.O.S.C.:
Acronym for "Controle Officiel Suisse de Chronometres," the most important Swiss testing office responsible for the functioning and precision tests of movements. Tests are conducted on each individual movement at different temperatures and in different positions for which a maximum gap of -4/+4 seconds per day is tolerated. Those that pass the specifications for being a chronometer are awarded a certificate.

Cotes de Geneve:
Surface decoration applied mainly to high quality movements, comprising an even pattern of parallel stripes, applied with a quickly rotating plastic or wooden peg.

Crown:
The part of the watch linked to the movement through the winding stem passing through a hole in the case that allows a wearer to wind and handset the watch. Motion transmitted from the user's fingers to the crown is forwarded to the movement through the winding stem, from this to the barrel through a series of gears and finally to the mainspring. For water proofing purposes, simple gaskets can be used in the crown and some crowns can be screwed into the case.

Curb Pins:
Two pins, which embrace the balance spring at its outer end near to its attachment. The pins are fixed to the regulator or index. The time of vibration of the balance is adjusted by alternating the position of the pins.

Detent:
A mechanism that prevents another part from operating at certain times or at one point in a cycle of operations.

Dial:
The face of a watch showing the time and other functions that may be displayed by hands, markers, discs, or through windows. Typically, the dial is made of brass, sometimes silver or gold. A skeleton dial has metal cut away from the dial exposing the movement underneath.

Ebauche:
The main assembly of a watch comprising the power, transmission, escapement, regulating, winding, and handsetting mechanisms. In short, the "works" without the case, hands, or dial.

End Stone:
See Jewel.

Engine-Turned:
Decoration of dials, rotors, or case parts performed by an engine-turning lathe, producing a variety of patterns. It is also known as guilloche.

Entry Pallet:
The receiving pallet, which receives impulses from the escape wheel teeth as they enter. The exit pallet, or discharging pallet, receives impulses as the teeth leave.

Escapement:
The part of the movement, which controls the release of the motive power. The escapement both controls the release of the driving force and also imparts energy (impulses) to the balance to maintain it in oscillation. The regularity with which this dual action takes place is controlled by the balance wheel and its spring.

Escape Wheel:
The last wheel in the going train, which permits "escape" of the motive force, giving impulse to the balance. It is alternately locked and released.

Exit Pallet:
See Entry Pallet.

Flinque:
Engraving on a dial or case, typically covered with a layer of enamel.

Fluted:
Decoration on surfaces of case bezels or dials comprising of parallel grooves.

Fourth Wheel:
The wheel in a watch that drives the escape wheel pinion to the arbor of which the seconds hand is attached.

Frequency:
The number cycles per unit of time, generally expressed in vibrations per hour (vph). In horology, it is the number of oscillations of a balance every two seconds or its vibrations per second.

Full Plate:
A watch caliber in which the top plate as well as the pillar plate, is a circular plate, with the balance mounted above the top plate.

Geneva Seal:
Distinction assigned by the Canton of Geneva to movements produced by watch firms of the region and complying with all the standards of high horology with respect to craftsmanship, small-scale production, working quality, accurate assembly and setting. The Geneva Seal is engraved on at least one bridge and shows the Canton's symbol, a two shield with an eagle and a key respectively in each field.

Glucydur:
An antimagnetic rustproof metal alloy comprising beryllium, nickel, and copper that expands very little when exposed to heat. These properties make glucydur useful in making balance wheels to ensure high accuracy of timekeeping.

Grand Sonnerie:
A watch which strikes both the hours and quarters at each quarter.

Guilloche:
Decoration of dials, rotors, or case parts performed by an engine-turning lathe, producing a variety of patterns. It is also known as engine turning.

Hairspring:
Another name for the balance spring.

Half Plate:
In a half plate movement, a section of the upper (top) plate is cut away to allow the balance to be mounted in the same plane as the plate, the balance, escape wheel, and fourth wheel having separate cocks.

Hand:
Analog indicator for the hours, minutes, and seconds as well as other functions.

Hour Wheel:
The wheel, which carries the hour hand.

Impulse:
The energy or "push" derived from the mainspring via the train and escapement and imparted to the balance to maintain its oscillations.

Incabloc:
Shock-absorber system to help prevent damage from shocks to the balance pivots. Its retaining spring system assures an elastic play of both jewels of the balance wheel, thus absorbing the movements of the balance staff pivots when the watch receives strong shocks.

Index Pins:
See Curb Pins.

Index Regulator:
A small lever having a shorter end which carries the curb pins and a longer end that passes over a scale to serve as an indicator of any alteration made in the position of the curb pins when regulating the watch by moving the index forward "S" or "R" ("slow" or "retard") or "F" or "A" ("fast" or "avant").

Isochronous:
Occurring in equal periods of time. A balance would be truly isochronous if the duration of the oscillations were the same whether the arcs were long or short. Factors that impair isochronous include the escapement, the play of the balance spring between the curb pins, faulty poising of the balance wheel and its spring.

Jewel:
Bearings in a watch movement made of ruby, sapphire, crystal, or synthetic ruby. Generally, the steel pivots of wheels turn inside jewels (mostly synthetic rubies) lubricated with a very thin layer of special oil. The jewel's hardness reduces wear to a minimum even over long periods of time (50 to 100 years). Most refined jewels have rounded holes and walls to greatly reduce the contact between pivot and stone. The quality of a watch is determined more on the shape and finishing of jewels rather than their number.

Ligne:
Also called line. A French and Swiss unit of measurement for indicating the size of a movement. A ligne = 2x25 mm.

Lubrication:
To reduce friction caused by the running of wheels and other parts, special low-density oils are used in the pivots turning inside jewels, the sliding areas between levers, and the spring inside the barrel, as well as numerous other parts of a movement.

Luminescent:
Materials applied on markers (such as hour and minute hands) emitting luminous energy previously absorbed as electromagnetic light rays.

Main Plate:
Metal platform having several tiers for the gear train.

Mainspring:
The spring, which stores and transmits the driving force of a movement.

Manual:
A mechanical movement in which winding is performed by hand.

Manufacture:
Said of a watch company that employs a movement in at least one of its models that it has manufactured itself on its own premises.

Module:
A self contained mechanism, independent of the basic caliber, added to the watch movement to make an additional function available, such as chronograph, power reserve, GMT, perpetual or full calendar.

Motion Work:
The gearing, which causes the hour hand to travel twelve times slower than the minute hand. It consists of the cannon pinion, minute wheel, and pinion and hour wheels.

Movement:
The main assembly of a watch comprising the power, transmission, escapement, regulating, winding, and handsetting mechanisms. In short, the "works" without the case, hands, or dial. Movements are divided into two great families: quartz and mechanical.

Nivarox:
Trade name of an antimagnetic steel alloy used for modern balance springs.

Oscillation:
Rotation cycle of the balance wheel.

Overcoil:
The last coil of a Breguet balance spring. See Balance Spring.

Pallets:
Part or parts of the escapement transmitting motive force to the balance, in order to maintain the amplitude of oscillations unchanged by freeing one tooth of the escape wheel at a time. In general, pallets are jewels and termed "pallet stones."

Perlage:
Surface decoration applied to plates, bridges, and rotors comprising an even pattern of partially overlapping dots, applied with a quickly rotating plastic or wooden peg.

Perpetual Calendar:
A calendar watch, which takes into account not only the short months, but also leap years, all without manual adjustment.

Pinion:
A small-toothed wheel that combines with a wheel and an arbor to form a gear. A pinion has less teeth than a wheel and transmits motive force to a wheel.

Pivot:
The extremity of a rotating arbor on which it is supported.

Plate:
A metal platform having several tiers for the gear train. See also Full Plate, Three Quarter Plate, and Half Plate.

Plated:
Said of a metal treated by a galvanizing process in order to coat a thin layer of gold or other precious metal on a brass or steel base.

Poise:
A balance is said to be in "poise" if it has no heavy point. Its equilibrium is unaffected by change of position.

Positional Error:
Changes in the rate of a watch when the watch is placed in different positions.

Power Reserve:
Time remaining (in hours) of a movement after it has reached the winding peak. The time remaining is typically displayed by an indicator on the dial.

Quarter Repeater:
A watch, which repeats the hours and quarters when a push-piece is depressed or a slide piece moved.

Rack:
A toothed segment.

Ratchet Wheel:
A saw-toothed wheel, in which the fronts of the teeth are radical and the backs straight lines. Used in conjunction with a click (pawl) and spring and fixed by a square hole to the barrel arbor. The click prevents the wheel turning in the unwinding direction.

Rate:
The timekeeping performance of a watch. The "daily rate" denotes the difference between two states of a timekeeper separated by an interval of 24 hours.

Recoil:
Backward movement of the escape wheel during the unlocking process. It occurs when the exit pallet presses a tooth of the escape wheel backward.

Regulator:
See Index.

Repeater:
A watch whose mechanism can be set in motion to denote the approximate time by hammers striking bells, gongs, or a block within the watch case.

Sweep Seconds:
A seconds hand pivoted in the center of the dial concentric with the hour and minute hands, and traversing the dial in one minute. Sometimes called a "center seconds."

Third Wheel:
The wheel between the center and fourth wheel.

Three Quarter Plate:
In a three quarter plate movement, a section of the upper (top) plate is cut away to allow the balance to be mounted in the same plane as the plate, the balance and escape wheel having separate cocks.

Timing screws:
See Balance Screws.

Tourbillon:
Abraham Breguet's device (patented in 1801) for neutralizing the positional (vertical) errors in a watch due to gravity and positioning of the watch to improve the watch's rate. In a tourbillon (from the French word for "whirlwind"), the entire escapement (balance, balance spring, escapement mechanism) is mounted in a revolving carriage or cage and rotated completely on its axis over regular periods of time, usually once a minute. Although this device is not absolutely necessary for accuracy purposes today, it is still appreciated as a complication of high quality watches.

Tourbillon carriage:
In a tourbillon device, the tourbillon carriage houses the balance, balance spring, and escapement and the carriage is rotated usually by one revolution per minute, thus compensating for all the possible errors over 360 degrees.

Vibration Frequency (vph):
In a watch, the balance wheel swings to and fro on its own axis and acts as the ruling organ of the movement's escapement. The amplitude (usually about 300 degrees) is restricted by the balance spring, which also provides the reversing of the direction of rotation. The frequency of the alternating vibration is measured either in vibrations per hour (vph) or Hertz (Hz). Until the 1950s, wristwatches worked mostly at a frequency of 18,000 vph (2.5 Hz); later, higher frequencies were adopted to produce a lower percentage of irregularities to the rate. Today's watches usually have a frequency of 28,800 vph (4 Hz), which assures a good precision standard and less lubrication problems than extremely high frequencies, such as 36,000 vph (5 Hz).