Extension Spring Dimensions

The notes on extension spring dimensions refer to diagram at bottom of page.  At Master Spring, we've been creating custom extension springs for more than 75 years.  Let us help you design and build the springs for your next application today.  Please call us at 708-453-2570 for a free quote.

Per Spring Manufacturers Institute Handbook of Spring Design 

d          wire diameter

I.D.      Inside Diameter

O.D.    Outside Diameter

D.        Mean coil diameter = (O.D. + I.D.)/2 or O.D. - d

Lf            Free Length = The distance between the inner surfaces of the ends.  It is equal to the spring body length plus ends, where spring body length is given by Lbody = d(N+1).  N = Number of Coils.