Ever since John Harrison first used them in his H4 pocket watch, to defeat the longitude problem, jewel bearings have played a pivotal role in the precision of nearly every serious watch or chronometer produced since. They are now so ubiquitous and commonplace that most watchmakers take them for granted. We shouldn’t. The time and energy – not to mention patience and precision – required to make a single jewel is incredible.
While George Daniels illustrates in detail how to cut and shape jewel bearings in chapter 7 of Watchmaking, there are subtleties to this art that are much better communicated through video. Thankfully, once upon a time, America’s Elgin National Watch Company produced a comprehensive, 72 minute documentary on the production of watch jewels, detailing every step of their process, from raw boule right through to the specular finish. If you have ever wondered just how a watch jewel is made, watch and learn:
I found the segment on the automatic drilling machine to be most insightful, particularly the way the fine, steel drill rod is set and centered in shellac without holding up production of the other stones being drilled simultaneously. It is also interesting to note the number of naturally sourced aids, such as olive oil and honey, that were used by Elgin in the production of their jewels. Having spent many long hours enlarging a jewel hole once, using Daniels’ techniques, I can attest that it is nothing short of the miracle of industrialization and economies of scale that allows synthetic ruby jewels to be as inexpensive and abundant as they are today.
To download a copy of the documentary to watch later, or to stream it in a different format, visit archive.org/details/JewelBearings.