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September 7th, 2007 - Jewels in Watches
The jewels that are usually used in watches are rubies, sapphires, garnets and diamonds. For ordinary consumers when they hear of watches in jewels they usually assume that the jewels referred to are the precious stones adorning the watch’s face and/or watch straps. The more visible stones adorning the watch the more valuable a watch is. While they are jewels ON watches when horologists talk about jewels IN watches what they are referring too are the jewels within the watch, which serve specfic functions.
The primary function of jewels is to help reduce friction. They are able to serve this function due to their smooth surface, which allows the metal parts to slide past them without rubbing into any rough surfaces. They are also very hard (especially diamonds) that they suffer from minimal wear and tear.
There are basically fur types of functional jewels: hole jewels, cap jewels, pallet jewels, and the roller jewel. They are differentiated not by their function since they all serve the same function, which is to reduce friction, but by their shape and the location in which they are placed. Hole jewels are, as the name implies, jewels that have holes. They are shaped like donuts and placed on wheel arbors. Cap jewels are flat and “cap” the end of arbors. Pallet jewels are rectangular bricks that are placed on the pallet fork. And last, the roller jewel is placed on the balance wheel.
Image Source: NAWCC