A circular metal circle which, together with the balance spring, embodies the regulating organ of a mechanical watch. It has a decisive influence on the accuracy of the watch's rhythm. The balance can be defined as an 'oscillating wheel' in static equilibrium. Bimetal balances were still used until the 1940s to compensate for temperature variations on precision clocks. After the self-compensating 'nivarox' balance spring had matured to the point where it was ready for series production in 1933, bimetal balances gradually became less important. They were increasingly replaced by monometallic 'glucydur' balances made of beryllium bronze. In combination with a nivarox balance spring, the glucydur balance was an ideal regulating organ that lost none of its importance in the following decades.

The balance spring can appropriately be described as the 'soul' of a mechanical watch. The inner end of this coil spring is attached to the balance staff; the outer end is connected by the balance spring pin to the balance cock. The elasticity of the spring ensures that the balance regularly oscillates back and forth. In combination with the moment of inertia of the balance rim, the active length of the balance spring determines the duration of each balance vibration. For this reason, most watches are equipped with an index that can be moved in infinitesimal increments to precisely alter the active length of the balance spring. Lengthening the active length causes the watch to run slower; shortening the active length causes the watch to run faster. The precision of mechanical watches also depends on the quality of the material and the shape of the balance spring. This spring is three to four times thinner than a human hair and weighs 2/1000 of a gram (0.002 g). Despite its extreme slenderness and feather-light weight, it is still able to withstand tensions equal to a weight of 600 grams. The thin coils of a spiral contract every year and expand more than 200 million times.

The elasticity of hardened steel balance springs varies with temperature. This causes corresponding changes in the speed of a watch. To counteract this effect, precision watches are equipped with a bimetal balance spring. Balance springs were first marketed under the name 'nivarox' in 1933. Nivarox, an alloy composed of several metals, enables the balance spring to compensate for temperature variations. All of today's top-quality wristwatches use nivarox balance springs in combination with monometallic glucide balances.

A small piece of metal, pinned or (in modern movements) glued to the outer end of the balance spring. The balance spring stud is attached (usually pinned) to the spigot or balance plate lug.

A specially shaped metal part in which at least one pin of a movable part of a watch turns. A bridge is screwed at both ends onto a plate, where the opposite end of the pin(s) is inserted. Bridges (also called 'bars') are usually named after the rotating parts they support, e.g. the centre wheel bridge or barrel bridge.

The barrel consists of a toothed disc and a cylindrical box. This latter is usually closed by a lid. The barrel rotates freely on its arbor. The main spring is wound inside the barrel. The toothed disc of the barrel meshes with the first pinion of the train of a mechanical clock.

A hole drilled to accept a pin of a gear train. In fine wristwatches and pocket watches, as well as in clocks, friction is reduced by inserting bearing jewellery into the holes that accept the rapidly rotating pivots of wheels and pinions. Simpler watches make do with simple holes drilled in plates, bridges or taps. However, this simpler solution has the drawback that the pivot holes soon enlarge through abrasion, especially if there is insufficient lubrication. This drawback can be remedied by inserting bushings, usually made of brass or bronze.

A silvery white, malleable metal extracted from beryl. Alloys containing beryllium are characterised by their unique hardness, strength and elasticity. Beryllium bronze is used in watches, e.g. to make scales. See also glucydur.

A term that can have a variety of meanings in watchmaking. Strictly speaking, it means that the ring is snapped in the center of a watch case to hold the glass. Often, however, the same word is also used to describe a rotating (usually metal) ring affixed to the front of a watch case.

Before the invention of the balance spring, high-quality mechanical watches were generally equipped with bimetal balance scales. The rim, which is cut close to the arms, is made of two metals (steel and brass) that have different coefficients of expansion when exposed to temperature changes. Changes in the moment of inertia of the balance compensate for thermally induced changes in the length of a hardened steel balance spring.

It has been a long tradition among watchmaking craftsmen to blue the surfaces of steel components. Blueing requires a great amount of sensitivity and experience. The parts to be burnished are placed in a small pan, which is then heated over fire. The surfaces of these parts acquire the desired color when their temperature rises to just under 300 degrees Celsius.

This alloy of copper and zinc is an important metal used in the manufacture of watches. Depending on the purpose for which it will eventually be used (such as for use as a plate), brass alloys may contain varying amounts of their constituent substances.

A popular, very elegant and classic shape for watch hands. A circular hole is located at the terminal end (near the tip) of a Breguet hand.

The decisive contribution to the optimisation of the balance spring was made by Abraham-Louis Breguet. This talented watchmaker recognised the importance of the terminal curve for the concentric 'breathing' of the balance spring. He debuted a type of spring that would later be known as the 'Breguet overcoil' in 1795. The distinguishing feature of this type of spring is its raised outer coil. This apparently minor detail improves the concentric development and thus the precision of the balance. Starting around 1860, Edouard Philips studied balance springs and their various forms. His research, which he published in 1861, is still valid today. The tables and graphs developed by this French mathematics professor served as an indispensable basis for the formation of subsequent balance springs.

The wheels of a clock movement are carried under individual bridges that are screwed to the bottom plate.