Pocket Watch - Jeweled Movements

Jeweled Movements

For more information, see Mechanical watch

Watches of any quality will be jeweled. A jewel in a mechanical watch is a small, shaped piece of a hard mineral. Ruby and sapphire are most common, although diamond, garnet, and even glass are often seen. Starting in the early 20th century, synthetic jewels were almost universally used. Before that time, low grade natural jewels which were unsuitable as gemstones were used. In either case, the jewels have virtually no monetary value.

The most common types of jewels are hole jewels. Hole jewels are disks (normally flying saucer shaped) which have a carefully shaped and sized hole. The pivot of an arbor rides in this hole. The jewel provides an extremely smooth and hard surface which is very wear resistant, and when properly lubricated, very low friction. Thus, hole jewels both reduce friction and wear on the moving parts of a watch.

The other basic jewel types are cap jewels, roller jewels, and pallet jewels.

Cap jewels are always paired with hole jewels, and always with a conically shaped pivot. For a properly designed hole and cap jewel system, the pivot will always rest as a pin point on a thin film of oil. Thus, a hole and cap jewel offer lower friction and better performance across different positions compared with simply a cap jewel.

The roller jewel, also called the impulse jewel or simply impulse pin, is a thin rod of ruby or sapphire, usually in the shape of a letter "D". The roller jewel is responsible for coupling the motion of the balance wheel to that of the pallet fork.

Pallet jewels interact with the escape wheel. They are the surfaces which, 5 times a second, lock the gear train of the watch and then transfer power to the balance wheel.

A jeweled watch should contain at least 7 jewels. The seven jewels include 2 hole jewels on the balance wheel, 2 cap jewels on the balance wheel, a roller jewel, and 2 pallet jewels.

More highly jeweled watches add jewels to pivots out from balance wheel, starting with the pallet fork, then the escape wheel, fourth wheel, third wheel, then finally the center wheel. Jeweling to the third wheel gives 15 jewels, jeweling to the center wheel gives 17 jewels. Thus, a 17 jewel watch is considered to be fully jeweled.

With American makers, however, it was common on low-end movements to jewel to the third wheel on only the top (visible) plate of the watch. This gives a total of 11 jewels, but looks identical to a 15 jewel watch unless the dial is removed. Since watches with 15 jewels and less are often not marked as to the jewel count, extreme caution must be exercised when purchasing movements which appear to be 15 jewels.

Additional jewels beyond 17 are used to either add cap jewels, or to jewel the mainspring barrel of the watch. Watches with 19 jewels, particularly those made by Elgin and Waltham, will often have a jeweled mainspring barrel. Alternatively a 19 jewel watch will have additional cap jewels on the escape wheel. 21 jewel watches commonly have cap jewels on both the pallet fork and escape wheel. 23 jewel watches will have a jeweled barrel and fully capped escapement. The timekeeping value of jewels beyond 17 for a time-only movement is often debated.

Complicated movements will often have additional jewels which do serve useful purposes.

Greater jewel counts are often associated with better quality watch movements. While it is true that expensive movements often have higher jewel counts, the jewels themselves are not the reason for this. The jewels themselves add essentially no monetary value, and beyond 17 offer a negligible improvement in timekeeping ability and in movement life. Most of the cost of a more expensive watch is associated with better quality finishing and, more importantly, with a greater number of adjustments.