Ever wondered why 15, 17, 21 jewel ? Why not 16, 18, 22 Where does the odd number come from??

This is just some information I thought maybe someone would be interested in. 

Most of the older Bulova jewelled watches are either 15,17, 21 or 23 jewel.  Most of these jewels are ruby or simulated ruby (grown in a laboratory), cut to size and a tiny hole drilled through the centre.  These jewels may be used on either side of the Centre, 3rd and 4th wheels as well as for the escape wheel .   And on the pallet fork their are usually two on the pivot points.

The  pallets that release the escape wheel are also ruby shaped like little chissels and there are 2 of them.

There is also usually one either side of the balance wheel (you know - that little wheel with the hair spring attached that looks like it has little screws around the edge - The one that runs backward and forward)

But where is the single jewel?   

Its under the balance wheel on a little plate attached to the balance staff, and it is a ruby shaped like a little pin which fits into the end of the pallet fork and transmits energy from the escape wheel to the balance wheel.  That is the single jewel that makes up the odd number.

If I have not explained that properly - I will draw several diagrams so that you can see what I mean.

If you think that I am incorrect at any point - then post a reply and let me know where I have gone wrong.

Happy Bulova

Janet

Stephen Ollman's picture
Stephen Ollman
Posted July 15, 2010 - 9:02pm

Club 5000Panel Member

Great post Janet. The jewels in a movement have always amazed me. The precision of these very fine pieces astounds me, especially the 2 pallet stone jewels. They are so tiny and perfectly cut!

See here: http://trusted-forwarder.org/elgin/help/watch_jewels.html for a great diagram of the placement of jewels on the average machanical watch.

syfre
Posted July 18, 2010 - 1:48pm

you are not wrong , but you may find some 16 jewels : just add a cap jewel on the escape wheel of a 15 jewels .

I think the record is an automatic waltham 100 jewels !

looks here

http://www.timezone.com/library/workbench/workbench0025