Mainsprings size

Discussion in 'Clock Repair' started by Anthony Landi, Jan 4, 2019.

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  1. Anthony Landi

    Anthony Landi Registered User
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    Nov 4, 2016
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    I have a Seth Thomas 48S in need of a time side mainspring. Can anyone tell me what size I would need? Going through Timesavers catalogue. It' s all quite confusing.
     
  2. Willie X

    Willie X Registered User

    Feb 9, 2008
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    It's best to measure the old spring. This is usually a better bet than going by a chart. Is the old spring still intact?
    Willie X
     
  3. kinsler33

    kinsler33 Registered User

    Aug 17, 2014
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    Find a micrometer or a suitable caliper and measure the thickness of the mainspring.. Then measure its width. As for its length, stretch the thing out as far as you can and use a tape measure to guess its length. You won't be able to measure the length of the central, tightly-wound section, so guess: maybe ten inches. It's not all that critical.

    If the mainspring isn't broken, however, make your life easier and look for other causes of trouble, because many Seth Thomas mainsprings are miserable to remove and replace. If the clock's not running properly, cleaning, pivot-polishing, and re-bushing would be the first order of business. Years ago I drove myself nuts replacing what I decided were old, "set" mainsprings on a Seth Thomas mantel clock. Fool thing finally responded to bushings on the escape wheel and the verge, even though those pivots looked fine.

    Mark Kinsler
     
  4. Anthony Landi

    Anthony Landi Registered User
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    Nov 4, 2016
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    Unfortunately the old spring snapped, is in two pieces and has since been discarded.
     
  5. Anthony Landi

    Anthony Landi Registered User
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    Nov 4, 2016
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    Thanks for the suggestions. Unfortunately the old mainspring is in two pieces and has since been discarded.
     
  6. shutterbug

    shutterbug Moderator
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    Oct 19, 2005
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    There is a mainspring chart somewhere here on the board or elsewhere on the internet that has many different models and the recommended springs for them. You might get fortunate and find yours there. Use search under the forums link at the top of the page.
     
  7. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
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    The chart I have says 0.750" x 0.012" x 90" time and 0.750" x 0.016" x 60" strike. Seth Thomas made quite a few variations of the No. 48 movement so don't know if this is correct for all or not.

    RC
     
  8. Willie X

    Willie X Registered User

    Feb 9, 2008
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    Any possibility of recovering the old spring? Long gone ... you will have to make a guess. RC gives you something to go by. You could order about 3 springs from .012" to .016" in thickness and use the one that gives you the most pleasant strike speed. Willie X
     
  9. John Rausch

    John Rausch Registered User
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    Mar 16, 2015
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    I know I'm late to the party, but I have a 48S that I am finishing up and I measured the springs as follows... Time = 0.685" x 0.014" x 74" and Strike = 0.750" x 0.020" x 63"
     
  10. TEACLOCKS

    TEACLOCKS Registered User
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    Mar 22, 2005
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