I have a Hamilton 940 that has a broken balance staff.

The movement serial number is 990631 can anyone advise which staff I need to get?

Thanks,
John

John,
Not sure which staff you need..Do you know if it is a large collet or a small collet..Single or double roller and the size of the pivot..If you can answer these questions we can then tell exactly which staff you need...

Gary, the watch is a double roller. Don't know collet size. The original question was "My balance staff is broken. Which staff do I need to replace it.

I am a new member so I am still trying to figure out how to properly use the site.

John

OK John that narrows it down some..The large and small collet has to do with the size of your hairspring collet..You have to know this because one will not work on the other..The staff number you need is a number 126 which is the double roller staff..

The 126 LC staff comes with a pivot size 10 (new number 607010)..

The 126 SC staff comes with the pivot size of 11 or 12 (new number 607011 and 607012).

Pivot size is important because if you get the wrong size pivot you might have to change the jewels to make the staff work..

John you can also see this if you go to (Hamilton Movement Numbers and Horological Reference Material)..

Click on that and in Lindell first post go down to (Direct Link to 1961 Parts and Material Catalog) Open that link and you will find the info you need under Balance staffs..

Thanks Gary. You have put me another step closer in figuring out what I need.

Have a great day.

John