Pocket Watch Jewels

Watch companies used semi-precious gems like garnets, rubies and sapphires as bearings to reduce friction for the steel pivots of the gear train, instead of softer bronze bushings. Learn the different kinds of jewels, their function and location, and how to determine the jewel count of a watch simply by looking at it.

The two primary types are hole and cap jewels, and both have functions on the balance assembly and in the gear train. Loose jewels are are those that have not been mounted in a setting. Think of the difficulty involved in making these tiny parts after mining the raw materials and cutting them into usable shapes.

Diamonds were used as cap jewels on the balance staff and on the escapement of the very highest grades. While they increase its value, the diamonds themselves do not increase its accuracy.

Which watch had the most?  Waltham's legendary Riverside Maximus came with 3 pairs of diamond jewels, for a total of six.

These stones were also mounted with shellac to the pallet fork, momentarily halting the gear train at every tooth of the escape wheel and pushing the balance wheel through its oscillations.

 It's the precisely angled faces of those two stones, driven by the mainspring, that impels the balance wheel into its next cycle.

Bushings are not jewels.

They are holes drilled into both upper and lower plates for the escapement, gear train and mainspring. The contact between all of the parts is metal on metal, and unless they're properly maintained the bushings will enlarge and become ruined.

These jewels were mounted in settings and then seated from the inside so they can't fall outward, fabricated with precision to end up flush with the plate surface. Friction keeps the setting tightly in place, so they're easily changed if necessary. This is also known as an "interference fit".

Sometimes called "smokestack" jewels, these settings were made of gold and were again screwed in from the top. The purpose of raised settings was partly for show, but they also did a better job of retaining oil because of their cupped shape, so that it didn't migrate onto the plates, staining them.

• 2 balance staff hole jewels
• 2 balance staff cap jewels
• 2 pallet stones (1 entry and 1 exit)
• 1 roller jewel 

Seven was the lowest total for the vast majority of American watches, and was the basis for all higher counts. There were no jewels in the gear train and the regulator is usually a simple one.

Several factories made 7-jewel watches with glass cap "jewels" on top of every pivot, along with false jewel counts and railroad motifs stamped on the plates. Underneath are  metal bushings, though the glass caps may keep a certain amount of dust out of the pivots. The micro-regulator on the balance is functional.

• 2 balance staff hole jewels
• 2 balance staff cap jewels
• 2 pallet stones
• 1 roller jewel
• 1 hole jewel for the pallet staff and the escape, 3rd, 4th, and center wheels, for a total of five

 Again, all of the gear train jewels are on the upper plate, with corresponding metal bushings on the pillar plate. 

• 2 balance staff hole jewels
• 2 balance staff cap jewels
• 2 pallet stones
• 1 roller jewel
• 1 pair of hole jewels for the pallet and the escape, 3rd, 4th, and center wheels, for a total of ten

All the components are jeweled except for the mainspring, which rotates too slowly to generate any appreciable friction.

• 2 balance staff hole jewels
• 2 balance staff cap jewels
• 2 pallet stones
• 1 roller jewel
• 1 pair of hole jewels for the pallet and the escape, 3rd, 4th, and center wheels, for a total of ten 
• 1 pair of cap jewels for the pallet, escape and 3rd wheels, and 1 on the 4th wheel, for a total of seven
• 1 pair of hole jewels for the mainspring barrel

Illinois was the only company to offer a 26-jewel watch, and roughly 250 of those were produced in just three grades: the Bunn Special, Benjamin Franklin and Pennsylvania Special.

Pennsylvania Special photo courtesy of Jones & Horan.