Glossary of watch terms
Know your watches! Here’s a glossary of watch terms designed to provided for a basic understanding of industry jargon.
Amplitude
Maximum angle by which a balance in a watch swings from its position of rest.
Analogue display
Indicates the passing of time by a marker (usually in the form of hands) on a scale on the watch dial.
Annual calendar
A watch showing the day, date, month and 24 hours, adjusting automatically for short and long months. The calendar needs setting only once a year - from the end of February to the 1st of March.
Aperture
Small opening in a watch. The dials of some watches (in French: montres à guichet) have apertures in which certain indications are given (e.g. the date, the hour, etc).
Arm-in-the-air watch
A scene or figure on a watch dial with parts that move to indicate the time in hours and minutes when a button is pressed.
Astronomical watch
A timepiece with any indication of time depending on the sun, moon or stars, such as equation of time, moon phase, sidereal time, sun hand, time of sunrise and sunset, zodiacs, and star disc.
Automatic watch
A watch whose mainspring is wound by the movements of the wearer's arm. On the basis of the principle of terrestrial attraction, a rotor turns and transmits its energy to the spring by means of an appropriate mechanism. This means the watch does not have to be recharged manually and, unlike a quartz movement, does not need a battery. The system was invented in Switzerland by Abraham-Louis Perrelet in the 18th century.
Balance
A wheel-like element in a watch which alternately rotates clockwise and counter-clockwise. It is connected to the gear train of a watch and designed to make the movement of the gear train as uniform as possible. Also called balance-wheel.
Barrel
Thin cylindrical box containing the mainspring of a watch. The toothed rim of the barrel drives the train.
Bezel
The retaining ring in which the watch’s crystal or glass is mounted. It forms part of the case and was usually hinged to the main body until about 1880, after which screw-threaded or snap-on bezels gradually came into use.
Calibre
Originally used to mean the size of a watch movement, this term now denotes a type of movement (men's calibre, automatic calibre, etc). When a calibre number is accompanied by the manufacturer's mark, it serves as an indication of origin.
Chime/Carillon
Watch mechanism to sound the time, usually by hammers striking gongs inside the case. A chime involving more than two gongs is called a carillon.
Chronograph
Watch or other apparatus with two independent time systems: one indicates the time of day, and the other measures brief intervals of time. Counters registering seconds, minutes and even hours can be started and stopped as desired.
Chronometer
Watch which has undergone a series of precision tests by an official institute in very unfavourable conditions.
COSC
Contrôle Officiel Suisse des Chronomètres. Switzerland's official rating bureau for chronometers.
Complications
Any horological function with the exception of the display of hours, minutes and seconds. Complicated watches are assigned to one of three categories: watches with one or several additional hands that have a timing function (watches with independent or jumping seconds, chronograph with minute registers or fly-back hands); watches with chimes (minute repeaters); and watches with astronomic indications (perpetual calendar, moon phases, equation of time). When a watch incorporates mechanisms of all three categories, it is referred to as a grand complication.
Dial
The “face” of the watch. It can be silvered, engine-turned (synonyms: guilloché, engraved), enamelled, gilded, lacquered, or set with precious stones.
Equation of time
The difference between mean solar time (our legal time with a consistent 24-hour day) and true solar time at any given time. This difference, which is compensated four times a year, ranges from about +14.5 minutes in February to about –16.5 minutes in November.
Escapement
Set of parts (escape wheel, lever, roller) which converts the rotary motion of the train into to-and-fro motion (the balance).
Fly-back date hand
In a chronograph with analogue display, an additional centre second hand which can remain superposed on the other one as it moves, can be stopped independently and then made to "fly back" so as to catch up with the other hand, can be stopped and reset to zero together with the other hand. An example is a hand which indicates the date against a scale and then flies back to the beginning of the month after reaching the 28th, 29th 30th or 31st day, according to the month and leap year.
Frequency
Defined by the number of oscillations per second. In quartz watches, the frequency is generally 32,768 oscillations per second. It is commonly expressed by the abbreviation Hz (Hertz).
Gear
A mechanism that transmits motion and force via toothed wheels.
GMT
Abbreviation of Greenwich Mean Time. GMT is a term sometimes used to describe a watch which indicates the time simultaneously in the world's different time-zones.
Gong
A tempered metal wire or blade which generates a tone when struck by a hammer. At one end, it is attached to the movement and the remaining length is freely suspended in a curve around the bridges. Sometimes called bell.
Hand
Indicator usually made of a light, thin piece of metal which moves around, or over, a graduated dial or scale. Watches generally have three hands to show the hours, minutes and seconds. Hands can have very different shapes: pear, Breguet (also called moon hands, they have a hole cut into a small disc near the point), sword, skeleton, baton, arrow, etc. The seconds hand (sweep or direct drive) can be mounted at the centre of the dial with the hour and minute hands, or on a small dial usually situated at 6 o'clock (small seconds). On a mechanical movement, the centre seconds hand generally jumps forward five times a second; on a quartz movement, only once a second.
Jumping hours
Digital hours on a disc appearing through an aperture in the dial. At the end of each hour the disc jumps forward to reveal the next numeral.
Lugs
An exterior part of the watch that extends from the case to hold the strap or bracelet. Also called horns.
Luminescence
Having the power to emit rays of light. A luminescent material is deposited on numbers and hands in order to read the time in the dark.
Mainspring
The driving spring of a watch or clock, contained in the barrel.
Manual watch
A mechanical watch wound by hand.
Minute repeater
A timepiece that can be made to strike the time in hours, quarters and minutes, by means of a push-piece or slide, usually in the side of the case.
Moon phases
The progression of visible changes in the moon’s appearance during its orbit around the Earth (new moon, waxing moon, half moon, full moon, waning moon).
Movement
The “motor” of a watch, an assembly consisting of the principal elements and mechanisms of a watch or clock: the winding and setting mechanism, the mainspring, the train, the escapement, the regulating elements.
Perpetual calendar
A complication that shows the day, date and month, correcting for months of different lengths and leap-years.
Pinion
Part mounted on the shaft of a wheel, the leaves of which engage the teeth of a neighbouring wheel.
Quartz
A common, crystalline mineral that comes in many forms, including citrine and opal, and can be found in many parts of the world.
Quartz movement
A Quartz Movement is a watch with a mechanism powered by a "quartz crystal". The crystal vibrates when placed in an electronic field, thus powering the watch. Most affordable watches today have quartz movements. Quartz watches are mostly battery operated.
Rotor
An unbalanced, semicircular pivoted mass inside an automatic or self-winding watch that swings with the movements of the wearer to wind the mainspring through a system of gears and ratchets.
Shock absorber
Resilient bearing which, in a watch, is intended to take up the shocks received by the balance staff and thus protects its delicate pivots from damage.
Sidereal time
Based on one rotation of the Earth against a position at an infinite distance in space. A sidereal second is 0.9972696 of a conventional second, and a sidereal clock gains 3.85 minutes a day on a standard clock, or 24 hours in a year.
Skeleton watch
Watch in which the case and various parts of the movement are of a transparent material, enabling the main parts of the watch to be seen.
Split second chronograph
Chronograph with two seconds-hands which rotate together. One of the hands (the fly-back) can be stopped independently to record an intermediate time and then be made to catch up with the other hand.
Stainless steel
Corrosion resistant steel of a wide variety, but always containing a high percentage of chromium. Stainless steel is highly resistant to corrosion attack by organic acids, weak mineral acids and atmospheric oxidation.
Stopwatch
Timekeeping instrument which can be used for measuring intervals of time. When this is done, the time display is partly or wholly lost until the hands are reset.
Striking-work
In a watch or clock, automatic or hand-operated mechanism that strikes the hours or rings an alarm-bell.
Tachometer
Instrument for measuring speed. In watch making, it refers to a timer or chronograph with a graduated dial on which speed can be read off in kilometres per hour or some other unit (see timer).
Termineur
French term for an independent watchmaker (or workshop) engaged in assembling watches, either wholly or in part, for the account of an "établisseur" or a "manufacture", who supply the necessary loose parts.
Timer
Instrument used for registering intervals of time (durations, brief times), without any indication of the time of day.
Titanium
A metallic element that has been used mainly in industry because of its lightness, strength and high melting point, but has in recent years been used in some jewellery, owing to the attractive range of colours that it acquires by being heated.
Tonneau
The shape of a watch-case like the cross section of a barrel with bulging sides and extending lugs.
Tourbillon
Device invented to eliminate errors of rate in the vertical positions. It consists of a mobile carriage or cage carrying all the parts of the escapement, with the balance in the centre. The escape pinion turns about the fixed fourth wheel. The case makes one revolution per minute, thus annulling errors of rate in the vertical positions.
Train
A specific set of wheels and pinions in a watch movement.
Triple Complication
A minute-repeater combined with a perpetual calendar and chronograph in a single watch.
Vibration
Movement of a pendulum or other oscillating element, limited by two consecutive extreme positions. The balance of a mechanical watch generally makes five or six vibrations per second (i.e. 18,000 or 21,600 per hour), but that of a high-frequency watch may make seven, eight or even ten vibrations per second (i.e. 25,200, 28,800 or 36, 000 per hour).
Watch material
Loose parts, components either for producing watches or for repairing them. In the latter case, they are often called "spare parts" or "repair material".
Water resistant
Made to prevent water from entering. Water-resistant case, watch-case whose joints are made to prevent moisture from entering.
Winding
Operation which consists of tightening the mainspring of a watch. This can be done by hand (by means of the crown) or automatically (by means of a rotor, which is caused to swing by the movements of the wearer's arm).
Posted August 01, 2009