broken watch mainspring

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  • #49739
    brianw
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    • Topics Started: 21
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    I’ve been working on clocks for a while now and have just ventured into pocket watches.
    I have a swiss pocket watch with a broken mainspring. I don’t know the make of the watch.
    The problem I have is that I can’t source a replacement spring. The dimensions of the spring are 1.68mm wide, 0.17 mm thick and the barrel internal diameter is 20.68 mm.
    My question is that if I can’t get hold of a mainspring, how acceptable is it to rivet the old spring back together to get the watch going again and if I did, is the repair likely to last?
    I can see everyone throwing up their hands in horror, but I’m only doing this to practice working on old watches. I’m not going to sell it.
    If anyone knows where I can get a mainspring in the UK that would be the best solution for me. I’ve tried cousins and watchpart.co.uk. Meadows and Passmore don’t sell watch mainsprings.
    Brian

    #63574
    bernie weishapl
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    • Topics Started: 58
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    I have two of my own watches that I have did that exact thing Brian. Couldn’t find a mainspring and since they were mine I just did it. Both are still running 4 yrs later. :D

    #63575
    brianw
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    • Topics Started: 21
    • Total Posts: 109

    Hi Bernie,
    Thanks for your reassuring response. I wasn’t sure what sort of reaction I would get. I found a company who had someone who was very helpful, but they couldn’t match the spring. I’ve ordered the nearest they could get, but if it isn’t strong enough I’ll go ahead and rivet the old spring and see how it works out.
    Brian

    #63576
    brianw
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    • Topics Started: 21
    • Total Posts: 109

    I tried riveting the old mainspring, but it just kept breaking up. I guess it was old and tired and just didn’t want to do any more work. I’ve sent it to the scrap yard in the sky…..
    I purchased two new mainsprings which were the correct thickness and width but too short. I riveted them together in an “S” shape, it that makes sense, then cut one of them to get the original length and riveted a new outer end.
    So far it is working well and keeping good time. I’m going to use this as my personal pocket watch for a while and see if it stands the test of time.
    I’ll follow this up in six months time and let you know if it is still working.
    Brian

    #63577
    bernie weishapl
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    • Topics Started: 58
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    Sounds like a plan. I have also did a couple that were just brittle and did the same thing. I have often wondered if I had heat treated them if that would have allowed the process to be more successful. Anyway like you they were both mine and both are still running fine. Let us know if it continues running ok.

    #63578
    mrroundel
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    • Topics Started: 3
    • Total Posts: 22

    brianw: Do you have a copy of Swartchild and Company’s catalog? I have one from 1951 and it is invaluable for finding the proper, or acceptable, replacement mainsprings for Swiss and American watches. If you don’t have one, and can locate one for a decent price, I’d say “snag it”. Good luck.

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brianwbroken watch mainspring