Jewel Pin
American Watchmaker and Jeweler (1892)
To set a jewel pin in the table roller (of American watches) correctly, is a difficult task. Where the jewel pin is broken off, you will often save much valuable time by examining the broken part with your glass and noting the exact location of the pin before disturbing it. In some movements the jewel pin will be set as in Fig 185, occupying about two-thirds of the hole, in another movement the pin will not occupy much over one-half the space, as shown in Fig 186. By using care in selecting a jewel pin of precisely the same size as the old one and in inserting it in the same place, nine out of every ten movements will be found mechanically perfect and the balance have a good motion if the escapement is perfect. Most watchmakers remove the table roller from the balance staff, in case the jewel pin is loose. This you will find unnecessary if you will make the following described tool and use as directed. Take a piece of copper wire about half the thickness of a common pin tongue and bend it as shown in Fig. 187, so that it will be about one and one-eighth inch long. Cut or saw a groove in the inside of the ends, sufficiently deep to hold on to the table roller, say one-fourth inch from the end. This can be easily bent to accommodate all sizes of tables. If you wish to soften the cement, to tighten or replace a new jewel pin, it is only necessary to slip on the copper wire, and hold the extreme outer end in the flame of a small alcohol lamp a few moments and sufficient heat will follow the copper wire to soften the cement. Care must be exercised to keep the pin in the proper position, and when sufficiently heated, remove the wire quickly and allow the table to cool. By use of this little tool there is no need of removing the table roller, and absolutely no danger of injuring the finest expansion balance, as the tool need not, and must not touch the balance. The end of this tool is held in the flame by a pair of soldering tweezers. Always use shellac for cementing the jewel pin in the table roller.
What Has Changed in the Last Century
The technique the American Watchmaker and Jeweler described in 1892 is still recognisable at a bench today: the roller jewel (now usually called the impulse pin or roller jewel) is a synthetic ruby set in the table roller, and shellac remains the standard cement, softened with heat and chosen because it lets the pin be adjusted or removed without harming the balance. What collapsed was the trade itself. The quartz movement, launched commercially with the Seiko Astron in December 1969, drove mechanical watches out of everyday use within a decade, and the corner watchmaker who repaired a broken jewel pin for a few cents largely disappeared with them; the skill survives in luxury servicing and in a small number of watchmaking schools. A jeweller reading this entry now is likely working on a collector's piece rather than a customer's only timepiece.
Written for this edition, 2026.