I did some research on jewel bearings and found an excellent article explaining the differences between functional, nonfunctional and useless jewels in a watch movement.
Written by Watch Blogger on June 5th, 2006 with
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As most of you will know jewels like ruby or saphire are used to reduce friction in the bearings of watches. While it is common belief that the more jewels there are the better the movement, this article explains how jewels have been added to watches just for marketing purposes, without providing any functional value.
There is an ISO standard which defines a functional jewel as a “jewel which serves to stabilize friction and to reduce the wear rate of contacting surfaces of the components of a timekeeping instrument” and a nonfunctional jewel as a “jewel used for purposes other than as defined in 3.2″ (ie a Functional Jewel). The author of the article provides some interesting examples of both functional and nonfunctional jewels and goes on to explain how watchmakers use jewels that are functional according to the ISO standard, but still useless, as they neither significantly enhance the performance nor the longevity of a watch.
It seems like the highest number of useful functional jewels a watch can have is 23, as shown by the example of a Hamilton Grade 923 movement. The author still doubts the value of jeweled barrels, so the actual number may be even less.
Written by Watch Blogger on June 5th, 2006 with
no comments.
Read more articles on Know How.
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