Glossary of Terms: Watches, Watchmaking and Horology
- Ebauche
- - A "raw" or unfinished movement.
- Elinvar
- - An alloy of nickel, chromium, manganese, tungsten and steel used in balances and springs which is "invariant" over a wide range of temperatures. Used to manufacture hairsprings which are resistant to temperature changes.
- Endshake
- - The slight freedom of vertical movement of a pivoted wheel or arbor in its bearing. See also "side-shake".
- Engine Turning
- - Decorative engraving, usually on a watch dial or case.
- Entrance Jewel
- - The first jewel of the pallet contacted by an escape wheel tooth.
- Equation of Time
- - The difference, over the course of a year, between time as read from a sundial and a clock. It can be ahead by as much as 16 min 33 s (around November 3) or fall behind by as much as 14 min 6 s (around February 12). It results from an apparent irregular movement of the Sun caused by a combination of the obliquity of the Earth's rotation axis and the eccentricity of its orbit. The equation of time is visually illustrated by an analemma.
- Escapement
- - That portion of the movement that allows the motive power of the watch to "escape" slowly and in a regulated fashion, thus keeping time.
- Fine Silver
- - Silver that is .999 fine or higher, meaning that it is 999 parts per 1000 pure silver.
- Fourth wheel
- - One of the wheels in the gear-train of a watch which transmits the power of the mainspring to the escapement. Usually the wheel which is geared to revolve once per minute and often used to carry the second hand of the watch.
- Fusee (or Barrel and Fusee)
- - A device intended to reduce the effects of uneven power as the mainspring winds down. The mainspring barrel is connected to the fusee, a conical intermediate wheel, with a tiny chain. The fusee is connected to the gear train. When the mainspring is fully wound, most of the chain is wound around the fusee all the way to the narrow end of the cone. As the watch runs, the chain unwinds down to the wide end of the fusee cone a the chain wraps around the mainspring barrel. This has the effect of equalizing the power transmitted to the gear train, because the lever arm of the chain pulling the fusee is shorter when the mainspring is fully wound, and longer when the mainspring is unwound. Some fusees use a system of springs and ratchets to provide "maintaining power" to the gear train during winding of the mainspring.
- Gear Train
- - The interconnected system of gears and pinions which transmits power from the mainspring to the escapement.
- German Silver
- - A composition of nickel, copper and zinc. One of many nickel-alloys used in the fabrication of watch cases. It contains no silver. Also known as Nickel Silver.
- Going Barrel
- - An arrangement of the mainspring barrel in which the barrel arbor is turned to wind the watch, and the barrel turns as the watch runs down. Motive power to the gear-train is (usually) provided by the engagement of the teeth on the barrel rim and the pinion of the center wheel. This arrangement means there is always tension on the mainspring, even during winding, so the gear train keeps "going." See also "Motor Barrel."
- Guard Pin
- - Also called "guard safety pin". A thin finger on the pallet fork which works in conjunction with the safety roller to prevent an "out of action" condition (sometimes incorrectly called "overbanking").
- Guilloché
- - Engraving with a repetitive pattern (lines, waves, circles, etc)