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Glossary of Terms: Watches, Watchmaking and Horology

Acrylic Crystal
- An acrylic crystal composed of plastic composite that is generally less expensive than a glass or mineral crystal. Sometimes called an "unbreakable" crystal, though this is a misnomer as they can definitely break. A high-quality acrylic crystal has optical properties very similar to glass.
Analemma
- In astronomy, an analemma (Latin for the pedestal of a sundial) is a curve representing the angular offset of a celestial body (usually the Sun) from its mean position on the celestial sphere as viewed from another celestial body (usually the Earth). For instance, knowing that Earth's average solar day is exactly 24 hours (by definition), an analemma can be traced by plotting the position of the Sun as viewed from a fixed position on Earth at 24-hour intervals for an entire year. The resulting curve resembles a figure 8. This curve is commonly printed on globes. See also "Equation of Time."
Ancre
- Swiss term for the pallet.
Annealing
- The act of heating and slowly cooling a metal in order to render it softer for the purpose of machining, or to relieve internal stress.
Arbor
- The axle of a wheel or gear that turns in a bearing or jewel; e.g. barrel arbor, winding arbor, pallet arbor, etc.
Atomic Time Standard
- Provided by the U.S. National Institute of Standards and Technology, Time and Frequency Division, Boulder, Colorado. Atomic time is measured through vibrations of atoms in a metal isotope. The result is extremely accurate time that can be measured on instruments. A radio signal transmits this exact time throughout North America and some 'atomic' watches and clocks can receive them and correct to the exact time.
Automatic Winding (also called self-winding)
- A mechanically powered watch that is wound by the motion of the wearer's arm rather than through turning the winding stem (manual mechanical). In response to this motion, a rotor turns and winds the watch's mainspring. If an automatic watch is not worn for a day or two, it will run down and need to be wound by hand to get it started again.
Balance Wheel
- The spring-governed oscillating wheel that governs the timekeeping accuracy of the watch. This is the part of the watch that oscillates at a steady rate to measure the time.
Balance Staff
- The arbor (or axle) for the balance wheel. The part that, unfortunately, often breaks when you drop your watch.
Band
- A generic term used to refer to the band that holds a watch on your wrist. The preferred terms are bracelet and strap, which more clearly describe the two major types.
Banking Pin
- Two pins, sometimes adjustable, which limit the side to side motion of the pallet fork. Adjusting the banking pin also controls the amount of slide of the escape tooth on the pallet jewel
Barrel
- Also called "mainspring barrel." Thin cylindrical "can" which holds the mainspring of a watch and provides the motive power to drive the gear-train, usually through the center wheel. See also "Motor Barrel" and "Going Barrel."
Bezel
- Part of the case. The ring or "frame" that holds the crystal in place.
Bow
- Part of the case. The loop to which a watch strap or chain is affixed. The part that may accidentally come off, allowing your precious watch to fall to the floor when you're pulling it out of your pocket.
Bracelet
- A bracelet is the flexible metal band consisting of assembled links, usually in the same style as the watchcase. Detachable links change the length of the bracelet. Bracelets can be made of stainless steel, sterling silver, gold, or a combination. See also strap.
Brake Spring (also called bridle, slip-spring, or safety-spring)
- The extension to the mainspring in an automatic watch which allows the mainspring to slip along the outer surface of the barrel to prevent over-winding.
Breguet
- Abraham Louis Breguet, 1747-1823. Horological genius and inventor, and one of the most famous watchmakers of all time. The name is also applied to a balance spring which has its outer coil raised above the body of the spring and curved inward.
Bridge
- Complementary part fixed to the main plate to form the frame of a watch movement. The other parts of the watch are mounted inside the frame (part of the "ébauche").

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