Tight cannon pinion caused an old mainspring to break

[steve1811uk]

Could a tight cannon pinion caused an old weakened mainspring to break when the hands are wound backwards when setting the time? Well that just happened to me and a NOS watch from 1950 that I had just serviced. I was setting the time and I heard the mainspring let go. Could it be coincidence or did I put some extra strain on the old blue steel mainspring? Needless to say the cannon pinion has now been loosened and a replacement mainspring ordered. So near but so far

[praezis]

No, not possible. The gears are not moving during hand setting (with pallet fork installed).

[steve1811uk]

Really? Then how does the seconds hand keep moving, or sometimes move backwards?

[praezis]

4 minutes ago, steve1811uk said:

Really? Then how does the seconds hand keep moving, or sometimes move backwards?

1) watch running normally

2) watch was stopped by a too tight cannon pinion

[steve1811uk]

I think it must just have been coincidence then. Luckily no damage caused except for the broken mainspring.