Spring Index in Compression Springs

• Compression Spring Design Resources – Spring Manufacturing

The spring index is the relationship between the mean diameter and wire diameter. The equation is shown below. This is a very important relationship to consider for manufacturing ease and cost control. As a general rule, the index should be above 3 and less than 20. Springs designed outside these limits increase cost and require more tolerance.

Springs with small indexes increase tooling wear and are more likely to require additional processing steps to ensure adequate life. Large index springs often require additional tolerance on both diameter and length.

Please contact the CSPI Spring facility nearest you for more information on spring index and other considerations of spring design.