Engineering and Tolerance

Learn About: Continuous Length Extension Springs

Continuous Length Extension Springs are an excellent choice for prototype development or maintenance applications


  • Wire Diameter and Outside Diameters Match Lee Spring’s most popular Stock extension spring dimensions from .125” (3.18 mm) to 1.125” Outside Diameter (28.58 mm)


  • Music wire with light oil coat
  • 302 Stainless Steel.

Lengths Offered

  • 12”
  • 24”
  • 36”

Continuous Length Extension Springs are designed to be cut to desired length by user to meet particular load requirement. Various loops or hooks can be formed on the ends using looping pliers or other appropriate instruments; as wire size increases, use different tools including a vise to hold the coil body and a pry bar to bend up the last coil.

How to Cut Continuous Length Extension Springs:

  1. Fold Spring 180° at desire length and cut. Cut shorter that needed by on-half the coil body diameter.
  2. Across from cut end, bend last coil up at 45° angle. To form double loop, bend last two coils up by 45°;do not use heat!
  3. Twist cut end of loop into center of coil body. This may require pliers. You may hav to twist past center to allow the loop to flex back.
  4. Cut end of newly formed loop to obtain any gap needed for mounting.

Special Calculations:

  • To determine the spring rate per inch of extension at the final cut length, use the following formula:
    Rate = K / N,
    K = Stiffness Factor as specified for the stock item
    N = “Number of Coils per inch” as specified for the stock item X Final Body Length in inches
  • To determine load at an extended length: multiply deflection by the spring rate, and add to the Initial Tension.

Lee Spring Part PDF