There are four main types of watch jewels.
- Hole jewels are donut-shaped and highly polished. They act as bearings for the pivot ends of the rotating staffs or arbors that hold the gears and pinions in place. Being much harder than the metal used for the plates, they don’t wear as quickly. Properly oiled they cause much less friction for the steel staffs than metal against metal. There are two styles of hole jewels: train and olive. Train jewels have a concave top to accept oil and a flat bottom. Olive jewels are mated with cap jewels and are convex on top and concave in the center of the bottom to hold oil.
- Cap jewels are placed on top of hole jewels to prevent staffs from moving up and down (end shake). Circular and flat on one side, the top is usually convex, but in older watches the cap jewels used for the bottom pivot of the balance staff (end stone) was often made of diamond – flat on one side and faceted on the outer side. This is critical for balance assemblies, but much less so for others.
- Pallet stones are rectangular and the end of the impulse discharging stone is often shaped slightly different from that of the receiving stone. They may be highly polished on all surfaces or just on the impulse face, discharging edge, and locking face.
- Roller jewels are impulse pins located on the roller table of the balance assembly that engage the lever end of the pallet fork. Some are shaped as round cylinders, some as oval cylinders, and some as half cylinders – round on the impulse side and flat on the inside surface. Roller jewels are highly polished.
Gemstones Used For Jewels
Early hole jewels were made of quartz, garnet, beryl, sapphire, and ruby gemstones. Natural gems have microscopic inclusions that might cause a polished watch jewel to crack or shatter under mechanical stress. Advertisements for higher quality American watches often stated “highest quality jewels” referring to those free of inclusions. In 1902 Auguste Verneuil invented the process for creating synthetic ruby and by 1907 these were being produced in commercial quantity. Free of inclusions, the first commercial application for synthetic gemstones was in the production of watch jewels.
Jeweled Watches
The number of jewels used in early watches varied with the type of escapement used and the whim of the watchmaker. The diamond end was popular with English watchmakers, but rarely used by American. Successful mass-production of watches began with the “Waltham” company in 1856. The jewel arrangements found in the majority of antique and vintage watches are:
- Seven jewels: most American watches had a minimum of seven jewels: a hole and cap jewel for both ends of the balance staff, a roller jewel, and both pallet stones. antiquescollectibles.suite101.com/article.cfm/how_a_mechanical_watch_works
- Eleven-jewels: These movements had the seven primary jewels, plus lower (back) hole jewels for the pivots of the pallet fork, escape, fourth, and third wheels. Sometimes eleven jewels were arranged with hole jewels on both ends of the pallet fork and escape wheel arbors.
- Fifteen jewels: The primary seven jewels plus hole jewels for the top and bottom pivots of the pallet fork, escape- and fourth wheel.
- Seventeen-jewels: Fifteen jewels plus a hole jewel at each end of the center wheel arbor.
- Twenty-one jewels: A cap jewel at each end of the pallet- and escape wheel staff pushes the count to 21. americanhistory.suite101.com/article.cfm/the_railroad_grade_pocket_watch
- Twenty-three jewels: These premium watches often include a cap jewel at the lower end of the fourth- and third wheel staffs.
- Twenty-five jewels: Such watches may have hole jewels for the barrel arbor or sometimes cap jewels for the top of the third and bottom of the center wheel arbors.
A “fully jeweled” watch has 17-jewels. These jewels affect the function of a watch and have a measured improvement over metal bearings (bushings). However, jewel counts above seventeen were proven to be effective marketing tools. While cap jewels on the lower pivots of train gears are not necessary and hole jewels on barrel arbors have no practical mechanical function, movements with more than 17 jewels were marketed as being superior.
Hole and cap jewels were mounted in settings of brass or gold and fixed to the watch plates by means of screws. For balance jewels this allowed the distance between the top and bottom pairs to be slightly adjusted to the balance staff to eliminate excessive up/down movement (end shake). For others it was simply to facilitate the manufacturing process. In the 1940’s jewel settings were replaced by friction settings – jewels pressed into recesses cut into the watch plates and bridges.
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