The colour on a die spring is shorthand for its load class. Useful — but only if you know which standard you're reading.
What the colours mean
Under the widely used ISO 10243 system, die springs are colour-coded by load class — light to extra-heavy — for a given hole and rod size:
- Green — light load (most travel, least force)
- Blue — medium load
- Red — heavy load
- Yellow — extra-heavy load (most force, least travel)
Some ranges extend this with an extra-light class (often light green) and an ultra-heavy class (often grey). Within one hole size, moving up the classes trades deflection for force: a heavier spring gives more force but can't travel as far before it's over-stressed.
Why colour alone isn't enough
Colour conventions are not universal. The Japanese JIS system assigns colours differently — it uses yellow for a light class, almost the reverse of ISO — and some individual makers (older Raymond codes, for instance) shift the classes again. A "red" spring from one system is not the same as a "red" spring from another.
Don't order by colour alone. Specify by hole diameter, rod diameter, free length, and the force you need at your working deflection — then the colour takes care of itself, whatever the standard.
How to specify a die spring
- Hole (bore) diameter and rod/pin diameter — these fix the spring's outside and inside diameter.
- Free length.
- Working deflection and the force required at that travel.
- Maximum deflection for the life you need — lighter classes tolerate more travel; heavier classes less.
Get those right and the spring drops into the pocket and delivers the force every cycle.
IMPEX supplies Steinel Normalien system springs across the full range of load classes. Tell us your pocket size and the force you need and we'll match the right spring — standard-agnostic.