• <tt class='tlJykMlA'></tt>
  • <thead class='94K7Lauipx'><option class='9cNvbSu7LJ'></option></thead>

    <em class='jepytdnyfeW3'><b class='oR1Ys12nk'><td class='6rzzLTN'></td></b></em>

  • <dl class='Td0EmkF'><b class='qoWhaibfJ9'></b></dl>

  • <span class='lS1G'></span>

    Sidebar

    Calculate the Length of an In-Barrel Mainspring

    A properly sized mainspring will fill half of the available area in the barrel. It is easy to calculate the dimensions of the barrel; you will need at least a fragment of the old mainspring to specify the appropriate thickness.

    Change the items in the yellow boxes and see the Results below.

    Calculator
    Mainspring Length
    Barrel Measurements:
    Inside Diameter of the Barrel:
    Diameter of the Barrel Arbor:
    Mainspring Thickness:
    Results:
    Needed Mainspring Length:
    Formula:
    LMS = 
    1
    2 x TMS
     x 
    pi x DB2
    4
     - 
    pi x DA2
    4
     )
    where,
    • LMS is the mainspring length
    • TMS is the mainspring thickness
    • DB is the inside diameter of the barrel
    • DA is the outside diameter of the barrel arbor

    This calculator, provided by Horology - The Index, is one in a series of repair calculations.