Spring Index

Written by Jerry Ratzlaff on . Posted in Fastener

spring compression 6Spring index, abbreviated as C, a dimensionless number, is the ratio between the spring and wire diameter for a helical spring.  This number tells how tight the springs coils are.  All wire sizes have a limit to the coil diameter being formed, too small there can be damage to the material.  A higher spring index has a smaller wire and a larger spring diameter.  A lower spring index has a larger wire and a smaller spring diameter.

 

Spring Index formulas

\(\large{ C = \frac{ D }{ d }  }\) 
\(\large{ C = \frac{ 2 \; r }{ d }  }\)

Where:

 Units English Metric
\(\large{ C }\) = spring index \(\large{ dimensionless }\)
\(\large{ D }\) = spring diameter \(\large{ in }\) \(\large{ mm }\)
\(\large{ r }\) = spring radius \(\large{ in }\) \(\large{ mm }\)
\(\large{ d }\) = wire diameter \(\large{ in }\) \(\large{ mm }\)

 

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Tags: Equations for Spring