Jewel bearing
A stone (English Jewel, French Pierre ) referred to in watchmaking a manufactured from precious stones stock. These bearings are eg perforated stones, cover stones, Rolling Stones, pallet stones and the ellipse in movements.
Properties
Stones as ruby or corundum are generally used instead of metal to minimize friction and wear. Rubies (synonym perforated bricks ) together with the metal pin of the wheels or the balance wheel bearing for watches because of their perforation. Jewels were developed in 1704 by the Swiss mathematician Nicolas Fatio.
Stones were formerly made of natural gemstones, while today consist of synthetic ruby corundum or other. They are (gray in the picture) is pressed into the bottom plate or bolted within a version of Gold (French Chaton ) and adjusted. The hemispherical indentation in a stone hole (without cover ) is called the oil reduction, which is used to hold the watch oil ( yellow in the figure ).
Stones of rolling bearings (eg in ball bearings of the rotor of an automatic watch ) are spherical or roll form. This Rolling Stones and the top stones are not perforated and will not be referred to as jewels.
Further be used in the inhibition (anchor pallet stones, levers stone) as a sliding bearing blocks. These were first used by Thomas Mudge, who invented the lever escapement in 1757.
Watch
A high-quality mechanical watch with manual winding requires at least 15 functional jewels:
- Ten perforated bricks (two each for the pins of balance, lever, escape wheel, fourth wheel and the third wheel )
- Two cap jewels for the balance
- Two pallet stones for the anchor
- A lever stone ( ellipse)
In addition, two cylindrical roller bearings for the barrel, two hole jewels for the minute and two capstones for anchor and escape wheel may be present. For complicated watches ( Grand Complication ), eg with automatic winding ( at least 4 stones for the ball bearing of the rotor), perpetual calendar, chronograph or Repetitionsschlagwerk increases the number of required stones. However, the number of stones says nothing about the quality of the movement (see finissage ).