Mean Coil Diameter

The Mean Coil Diameter (D) of a spring is the Outside Diameter minus one wire diameter (d).

And, the Mean Coil Diameter (D) is also the Inside Diameter (ID) plus one wire size (d).

D = OD - d

D = ID + d

In spring design, the Mean Coil Diameter is used more for calculating the rate and ultimate stress in the spring rather than for fit.

The most practical method for measuring Mean Coil Diameter is to measure the Outside Diameter and subtract one wire size.

Please contact the Newcomb Spring facility nearest you for more information on calculating mean coil diameter and other considerations of spring design. Newcomb Spring also offers a special technical guide on CD that includes an animated glossary and information on spring characteristics. To request one of our technical cds, visit our Quick Contact page (please write that you are requesting a CD in the Notes field).