Mainspring Replacement Seth Thomas

Discussion in 'Clock Repair' started by dalesr, Dec 3, 2013.

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  1. dalesr

    dalesr Registered User

    Jan 4, 2009
    New Jersey
    Country Flag:
    I have a Seth Thomas Movement A400-000 that needs a Time Mainspring. I know that the Hermle Replacement movement for the A400-000 is Hermle 350-020 movement. Can I use the replacement mainspring for the 350-020 movement for my A400-000 movement? The A400-000 Time barrel is stamped with 8E and the dimensions of the barrel are shown below. I do not know the inner diameter of the Time Barrel on the 350-020 movement so I cannot compare inner barrel diameters.

    A400-000 movement
    Time Barrel Stamped "8E"
    38 mm barrel inner diameter
    10 mm arbor diameter
    Old mainspring 45/64, 42 in length, and .014

    Hermle 350-020 movement
    43/64 width
    47 1/2 length
    .0165 strength
  2. shutterbug

    shutterbug Moderator
    NAWCC Member

    Oct 19, 2005
    Self employed interpreter/clock repairer
    North Carolina
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    That's probably a question for Mark Butterworth. I know some of the replacement movements require a weight change, so I would be suspicious of switching out springs.

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