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When your stamping die, injection mould, or punch press demands consistent, repeatable spring force, a worn or mismatched spring becomes a costly liability. Engineers and toolmakers who work with tight-tolerance tooling need a compression spring that delivers predictable medium-load performance cycle after cycle — without premature fatigue or dimensional drift.
These Red TM die springs are colour-coded red to indicate medium load duty, conforming to the ISO 10243 / JIS B 5012 standard for rectangular-wire die springs. Each spring is wound from high-grade chromium-silicon alloy steel (SCr / SiCr wire), with outer diameters ranging from 8 mm (≈ 0.31 in) to 50 mm (≈ 1.97 in) and free lengths from 15 mm (≈ 0.59 in) to 350 mm (≈ 13.78 in). The red colour band identifies the medium load series, which typically delivers a spring rate in the range of 3–30 N/mm depending on size — suitable for the majority of standard die and mould applications.
Typical use cases include: die-set stripper plates in progressive stamping tools, ejector return mechanisms in plastic injection moulds, and spring-loaded clamping fixtures on CNC machining centres. Long-tail search terms that describe this product: rectangular wire compression spring for die sets, ISO 10243 red medium load mould spring, SiCr alloy die spring OD 8mm to 50mm.
Red designation follows ISO 10243 / JIS B 5012 colour coding, making it straightforward to identify load class at a glance during assembly and maintenance.
Wound from rectangular-section chromium-silicon alloy wire, providing a higher load capacity per unit length compared to round-wire springs of the same envelope size.
Fourteen outer diameter options (8 mm × 4 mm ID through 50 mm × 25 mm ID) combined with free lengths from 15 mm to 350 mm cover the vast majority of standard die and mould pocket specifications.
Springs are shot-peened and surface-treated to extend fatigue life and resist oxidation in typical workshop and production environments.
Manufactured to tight free-length and load tolerances, ensuring uniform spring force across matched sets — critical for balanced stripper plates and multi-cavity moulds.
Order exactly the quantity you need — single replacement springs or matched sets — without being forced into bulk packs that tie up toolroom inventory.
| Standard | ISO 10243 / JIS B 5012 |
|---|---|
| Load Class | Medium Load (Red) |
| Wire Material | Chromium-Silicon Alloy Steel (SiCr) |
| Wire Section | Rectangular |
| Outer Diameter (OD) Range | 8 mm – 50 mm (≈ 0.31 in – 1.97 in) |
| Inner Diameter (ID) Range | 4 mm – 25 mm (≈ 0.16 in – 0.98 in) |
| Free Length Range | 15 mm – 350 mm (≈ 0.59 in – 13.78 in) |
| Spring Rate (typical range) | See variant options |
| Max. Deflection Ratio | Typically 30–40% of free length (medium load) |
| Surface Treatment | Shot-peened; oxidation-resistant coating |
| Colour Code | Red |
| Quantity per Order | 1 piece (per variant selected) |
Measure the spring pocket bore in your die plate — the OD of the spring should be 0.5–1 mm smaller than the pocket bore for a sliding fit. The free length should be selected so that the spring is pre-compressed by 10–15% at the closed (working) position, and the total deflection at full stroke does not exceed 30–40% of the free length for medium load springs. Refer to your tooling drawing for pocket depth and stroke data.
Under ISO 10243 / JIS B 5012, die springs are colour-coded by load class: yellow = light load, red = medium load, blue = heavy load, and green = extra-heavy load. Red medium-load springs offer a balanced combination of deflection range and load capacity, making them the most widely used class in general stamping and moulding applications. If your application requires higher force in the same envelope, consider the blue heavy-load series.
Yes. These springs are wound from chromium-silicon alloy (SiCr) rectangular wire and shot-peened to improve fatigue resistance. When operated within the recommended deflection range (≤30–40% of free length for medium load), they are designed for extended production cycles consistent with standard ISO 10243 die spring service life expectations. Exceeding the rated deflection significantly reduces fatigue life.
The springs receive a surface treatment (shot-peening plus protective coating) that provides moderate corrosion resistance suitable for typical workshop conditions. For applications with continuous coolant exposure or aggressive chemical environments, consider applying a light oil film during storage and installation, or contact us to confirm suitability for your specific conditions.
Yes, provided the OD, ID, and free length match your existing spring. These springs conform to ISO 10243 / JIS B 5012 standard dimensions, which are interchangeable with springs from other manufacturers that follow the same standard. Always verify the load class (colour code) matches — substituting a different load class will change the spring force and may affect part quality or tool life.
For maintenance and replacement, ordering the exact number of springs needed keeps toolroom inventory lean. For new tooling builds, order matched sets from the same batch where possible to ensure consistent spring rates across all positions. If you need bulk quantities or matched sets with tighter load tolerances, contact us to discuss your requirements.
For medium-load (red) die springs, the maximum recommended working deflection is typically 30–40% of the free length. Operating beyond this range accelerates fatigue and can lead to premature spring failure. For example, a 100 mm free-length spring should not be deflected more than 30–40 mm in normal service. Always design your tooling to keep deflection within this range for reliable long-term performance.
