10BZAC Mainspring

Submitted by wdschell on January 10, 2021 - 5:55pm

Hello All,

I picked up a M1 Bulova at a thrift shop and everything looks really good and is running.  I put it on the timegrapher and the amplitude is only around 200 degrees.  Is that normal for these? I have only fixed a couple of elgin pocket watches up to this point and they had much higher amplitudes.


If it isnt normal do you all know what mainspring would fit this movement?  Thanks

Posted January 11, 2021 - 7:27am

I'm not too sure about the appropriate amplitude range (would also like to know, I have one of these that will not run more than a day); but I believe these use a sealed lifetime barrel, so you would need to find a barrel complete and not just a mainspring - Bulova part# 1S (also used by the 10BZACD)

Posted January 12, 2021 - 8:01pm

In reply to by Andersok

Oh, awesome.  I might try to just take it apart clean it and oil it and see if that helps anything.  Hopefully if I need to I can find that part.  Mine only runs for about 30 hours.  

I wore it for 2 days after I got it and it never stopped but once I took it off it ran for 30 and stopped.