Are alloy mainsprings really unbreakable under normal use?

ANS NO

This was possibly compromised the day it was built. Nice

Chris on a rare occasion I have had a complete failure of an alloy mainspring just like your example. The mainspring broke on the initial winding and it broke in multiple pieces. I was very surprised when I lifted the barrel cap off and saw the destroyed mainspring. Didn't expect that, but it can happen.

Rob
www.pocketwatchrepairs.net

Hi Rob,

I had a few new alloys have a single break within the first few days, but this is only the second one I have seen fail so dramatically, bet it would sound quite interesting to hear!!