Die Springs — ISO 10243 Color-Coded

Chrome Silicon Alloy Wire (SWOSC-V)

All die springs use chrome silicon alloy wire (SWOSC-V or equivalent), heat-treated to HRC 48-52. This alloy provides the optimal combination of high tensile strength (1,900-2,100 MPa) and fatigue resistance required for millions of compression cycles. The rectangular wire cross-section is the key differentiator from round wire springs — it maximizes the material's load-bearing capacity within a given outer diameter envelope, delivering 30-50% more force than a round wire spring of the same size.

Color = Deflection Limit = Fatigue Life

The color code is not arbitrary — it directly maps to the spring's maximum safe deflection ratio. Exceeding the rated deflection by 5% reduces fatigue life by approximately 10×. This is because stress in the wire increases exponentially near the deflection limit, accelerating fatigue crack initiation at the wire surface. The ISO 10243 safety rule: always select one color class above the calculated minimum — this provides the recommended 20% safety margin.

JIS vs Inch: Dimensional Standards

JIS (Japanese Industrial Standard) and Inch (NAAMS/North American) springs use different dimensional series but identical material and heat treatment. JIS springs use metric hole sizes (Ø10, Ø12, Ø14...) while Inch springs use imperial bore sizes (3/8 inch, 1/2 inch, 5/8 inch...). Load class color coding is universal across both standards — a 'red' spring from MISUMI JIS and a 'red' spring from Lamina Inch have equivalent load characteristics relative to their respective bore sizes.