Expertise

See Double Chronopraph.

This is the effort of a watchmaker to set the watch mechanism so that its daily gain or loss is as small as possible – a sort of fine-tuning. When a watch runs accurately it is said to be well regulated.

The ‘repetition’ in a small watch or clock is a striking mechanism that chimes the last hours recorded by the timepiece. The mechanism is normally activated by pressing a button or switch. There are various kinds of ‘repeater’ mechanisms.

The quarter hour repeater strikes a deep tone for the hour and a deep tone combined with a higher ones for the quarter hours.

The five minute repeater strikes the hours, the quarter hours and also each five minutes.

The minute repeater strikes the hours, the quarter hours and also the minutes (See also ‘minute repeater’).

The ‘reserve du marche’ is effectively the period of time it takes for a fully wound watch mainspring to run down to the point of near zero tension at which the watch will stop. Modern watches take much longer to run down than earlier models that were powered by a simple steel spring. There are some watches that have a special display on the facia to show the actual level of the tension reserves in the mainspring. This display is for many watch lovers an additional point of attraction.

The semicircular weight built into an automatic winding mechanism of a watch is known as the ‘rotor’. Activated by a mixture of inertia and gravity, this weight is made to swing around its shaft, every time the wearer moves his or her arm. With each swinging movement it tensions the mainspring. The forces are transmitted from the rotor to the spring via a gear system on the mainspring barrel and a crown-wheel. The wheel is normally located at the bearing of the rotor, but it is also sometimes to be found on its outer edge. If the rotor is designed to wind the mainspring with its movement in either direction, an additional intermediate wheel must be fitted. The final wheel in the automatic winding system is the ‘ratchet wheel’ on the mainspring housing. Since the mainspring of an automatic watch is almost constantly being wound up by the rotor weight, the outer end if the spring is not permanently fixed to the barrel (as is the case with many manually wound watches). Instead, a device named a ‘bridle’ and a special lubricant is used to allow the spring to slip slowly forward whenever it is necessary. This prevents the spring from being over-wound.

The ruby is a red coloured ‘corundum’ gemstone. In watchmaking, rubies are used as bearings, as cap-stones, as fulcrums and for the pallets of the anchor lever. Many years ago real rubies were used, but today only synthetic stones are used.