Post by Lalbert1Post by MikeMechanical watches always have an odd number of jewels. The jewels are used
as bearings for the gears, so they should be in pairs.
What's the leftover jewel used for?
I think the jewel that causes the number to be odd is probably the roller
jewel. For a description with illustrations of the location of the watch
"The jewels are located throughout the watch at key spots. The following are
The basic 7 jewels are part of the escapement and balance and are found on all
Elgin watches. They include cap and hole jewels for both the top and the bottom
of the balance wheel (total of 4), the two pallet jewels and the roller jewel.
The next 8, making 15 jewels, are hole jewels for the fast moving part of the
gear train.
The next 2, making 17 jewels, are jewels on the center wheel.
The next 2-4, making 19-21 jewels, are cap jewels on the escape wheel and the
pallet fork."
As you say, they seem to come in pairs, with the roller jewel being the single
common jewel for all jewelled watches.
Les
That's an interesting page, and one of the links provided there,
http://www.timezone.com/article.aspx?id=workbench&articleId=workbench0025
provides a detailed discussion of how watch makers have been less than
scrupulous in jeweling their watches, often adding non-functional jewels to
the movements at less cost than adding functional jewels, then being able
to label the watch 17, 19, or 21 jewels... The article starts off
discussing the Waltham 100 jewel movement, achieved with 83 jewels added to
the edge of the rotor in an automatic watch movement. Underneath that was a
conventional 17 jewel movement...
-- Mike --