My Watch Blog

Glossary

Alarm

Alarm — a bell or buzzer that can be set to go off at a given time.

Automatic winding

In order to eliminate the need to wind the watch, this device winds the watch’s mainspring automatically using the natural motions of the wrist, with a rotating-weight mechanism.

Balance spring

A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, working together with the balance wheel, controls the speed of movement of the parts in the timepiece. The regulator lever is used to adjust the speed so that the timepiece keeps accurate time.

Balance wheel

The balance wheel is the timekeeping device used in mechanical watches. It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel (called a ‘tick’ or ‘beat’) allows the gear train to advance a set amount, moving the hands forward. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or ‘tick’ very constant, accounting for its near universal use as the timekeeper in mechanical watches to the present.

Calendar

Calendar—displays the date, and often the weekday, month, and year. Simple calendar watches do not account for the different lengths of the months, requiring the user to reset the date 5 times a year, but perpetual calendar watches account for this, and even leap years. An annual calendar does not make the leap year adjustment, so the date must be reset on March 1 every fourth year.

Chronograph

Chronograph—a watch with additional stopwatch functions. Buttons on the case start and stop the second hand and reset it to zero, and usually several subdials display the elapsed time in larger units.

Complications

Additional functions on a watch besides the basic timekeeping ones are traditionally called complications.

Escapement

In mechanical watches and clocks, an escapement is a device which converts continuous rotational motion into an oscillating or back and forth motion. It is the source of the “ticking” sound produced by watches and clocks.

Hacking feature

Hacking feature — found on military watches, a mechanism that stops the second hand while the watch is being set. This enables watches to be synchronized to the precise second. This is now a very common feature on many watches.

Mainspring.

A mainspring is a spiral torsion spring of metal ribbon that is the power source in mechanical watches and some clocks. Winding the timepiece, by turning a knob or key, stores energy in the mainspring by twisting the spiral tighter.

Mechanical watch.

A mechanical watch is a watch that uses a non-electric/electronic mechanism to measure the passage of time. It is driven by a spring (called a mainspring) which must be wound periodically, and which releases the energy to activate the balance wheel, which oscillates back and forth thanks to the balance spring at a constant rate, transmitting the impulse through the lever escapement to the gear train, that divides the impulse into hours, minutes and seconds, thus making a ‘ticking’ sound when operating.

Moon phase dial

Moon phase dial—shows the phase of the moon with a moon face on a rotating disk.

Movement.

In horology, a movement is the internal mechanism of a clock or watch, as opposed to the case, which encloses and protects the movement, and the face which displays the time.

Regulator lever.

In order to adjust the rate, the balance spring usually has a regulator, a moveable lever with a narrow slit on the end through which the last turn of the spring passes. The portion of the spring after the slit is held stationary, so the slit controls the usable length of the spring. Moving the regulator slides the slit up or down the spring, changing its effective length. Moving it away from the spring’s attachment point (stud) shortens the spring, making it stiffer, increasing the balance’s oscillation rate, and making the timepiece gain time.

Repeater

Repeater — a watch that chimes the hours audibly at the press of a button. This rare complication was originally used before artificial lighting to check what time it was in the dark. These complex mechanisms are now only found as novelties in extremely expensive luxury watches.

Skeleton watch.

A skeleton watch is a mechanical watch, in which all of the moving parts are visible through either the front of the watch, the back of the watch or a small cut outlining the dial.

Tourbillon

Tourbillon — this expensive feature was originally designed to make the watch more accurate, but is now simply a demonstration of watchmaking virtuosity. In an ordinary watch the balance wheel oscillates at different rates, because of gravitational bias, when the watch is in different positions, causing inaccuracy. In a tourbillon, the balance wheel is mounted in a rotating cage so that it will experience all positions equally. The mechanism is usually exposed on the face to show it off.

Watch jewels

Jewel bearings are used to reduce friction. The advantage of using jewels is that their ultrahard slick surface has a lower coefficient of friction with metal. The static coefficient of friction of steel-on-steel is 0.58, while that of sapphire-on-steel is 0.10-0.15. Jewels in modern watches are all synthetic sapphire or (usually) ruby. The only difference between sapphire and ruby is that different impurities have been added to change the color; there is no difference in their properties as a bearing.

Wind indicator or power reserve indicator

Wind indicator or power reserve indicator — mostly found on automatic watches, a subdial that shows how much power is left in the mainspring, usually in terms of hours left to run.