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When a mold or die-tooling project demands consistent, repeatable spring force without premature fatigue failure, engineers and toolmakers reach for a spring that can handle the cycle count. TM red-coded compression die springs are rated for medium load applications, making them the go-to choice for injection mold ejector systems, stamping dies, and precision jig fixtures where force consistency matters every cycle.
Each spring is manufactured from high-fatigue chromium-silicon alloy wire, wound to close tolerances and finished in a distinctive red coating that identifies the medium-load rating at a glance. Outer diameters span 6 mm (0.24 in) to 60 mm (2.36 in); inner diameters run at approximately 50 % of OD (e.g., 3 mm ID for 6 mm OD, up to 30 mm ID for 60 mm OD). Free lengths range from 15 mm (0.59 in) to 175 mm (6.89 in) across the available variants.
Typical use cases include: injection mold ejector-plate return springs for automotive and consumer-electronics tooling; blanking and forming die stripper springs in sheet-metal stamping operations; and precision fixture clamping springs in machining and inspection jigs where controlled deflection under medium loads is critical.
| Load Class | Medium Load (Red) |
|---|---|
| Standard | ISO 10243 / JIS B 5012 |
| Material | Chromium-Silicon (Cr-Si) alloy spring wire |
| Surface Finish | Red epoxy coating |
| Outer Diameter (OD) | 6 mm – 60 mm (0.24 in – 2.36 in) |
| Inner Diameter (ID) | See variant options |
| Free Length | 15 mm – 175 mm (0.59 in – 6.89 in) |
| Spring Rate | See variant options |
| Max. Deflection | See variant options |
| End Type | Closed & ground (flat ends) |
| Coil Direction | Right-hand wound |
| Quantity per Order | 1 piece |
Measure the pocket bore diameter in your mold or die plate — this is your maximum OD. The spring OD should be 0.5 mm to 1 mm smaller than the pocket bore to allow free movement. The inner diameter must clear the guide pin with at least 0.5 mm radial clearance on each side. Use the Size (Outer Dia. × Inner Dia.) option above to match your pocket and pin dimensions.
Per ISO 10243 and JIS B 5012, die springs are color-coded by load class: light load = yellow, medium load = red, heavy load = blue, extra-heavy load = green. Red (medium load) springs offer a balanced combination of deflection range and force output, making them suitable for ejector-plate return, stripper-plate actuation, and general clamping applications where neither maximum force nor maximum travel is the sole priority.
These springs are wound from chromium-silicon (Cr-Si) alloy wire. Cr-Si alloy has a higher tensile strength and better relaxation resistance than standard carbon-steel (e.g., SWC/SWP) wire, which translates to longer fatigue life at equivalent stress levels. This makes them well-suited for high-cycle injection molding and stamping operations where springs may compress millions of times before replacement.
Yes. The OD and free-length dimensions follow ISO 10243 / JIS B 5012 standard series, so they are dimensionally interchangeable with other ISO-compliant medium-load (red) die springs. Always verify the OD, ID, and free length against your tooling drawings before installation to confirm fit.
Determine the required working load (force at compressed length) and the available stroke (deflection). Divide the working load by the spring rate for the selected size to get the required deflection. Add the compressed length to the deflection to get the minimum free length needed. Apply a pre-load of 10–15 % of the maximum rated deflection to keep the spring seated during operation. If you need assistance with spring rate data for a specific variant, contact us to confirm.
Inspect springs at each scheduled mold or die maintenance interval. Look for visible coil cracking, permanent set (free length shorter than nominal by more than 3 %), or surface corrosion that has penetrated the coating. Replace any spring showing these signs immediately. Lubricate the guide pin lightly with a compatible grease to reduce friction-induced wear on the ID coils. Store spare springs horizontally in a dry environment away from solvents that could degrade the epoxy coating.
Yes. While designed to die-spring standards, these Cr-Si compression springs are also used in industrial machinery, hydraulic valve assemblies, jig and fixture clamping, and automation equipment wherever a compact, high-fatigue compression spring with a known load class is required. Confirm that the spring rate and deflection range suit your specific load and travel requirements before use outside of tooling applications.
