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When a worn or undersized spring causes your press tool, injection mould, or fixture to misfire, the entire production run stops. Engineers, toolmakers, and serious DIYers who work with precision machinery need compression die springs they can spec with confidence — and that is exactly what these OD 8mm ID 4mm mould die springs deliver. Available in five colour-coded duty ratings from Extra Light to Super Heavy, you can match spring force to your exact load requirement without guesswork.
Each spring is manufactured from spring steel with an outer diameter of 8mm (0.315 in) and an inner diameter of 4mm (0.157 in). Free lengths range from 15mm (0.59 in) to 100mm (3.94 in), and the colour coding follows the ISO 10243 / JIS B 5012 standard: Yellow (Extra Light), Blue (Light), Red (Medium), Green (Heavy), and Brown (Super Heavy). Wall thickness is typically 2mm. Available in packs of 1, 4, or 10 pieces.
Typical applications include injection mould stripper plates, stamping and blanking die return springs, jig and fixture clamping systems, and light-duty mechanical assemblies requiring consistent return force. Long-tail use cases include CNC router hold-down clamps, 3D-printer bed levelling mechanisms, and custom spring-loaded tooling for small-batch fabrication.
| Outer Diameter (OD) | 8mm (0.315 in) |
|---|---|
| Inner Diameter (ID) | 4mm (0.157 in) |
| Wall Thickness | Typically 2mm |
| Free Length Range | 15mm – 100mm (0.59 – 3.94 in) |
| Material | Spring Steel |
| Duty / Spring Rate | See variant options (Yellow / Blue / Red / Green / Brown) |
| Colour Coding Standard | ISO 10243 / JIS B 5012 |
| Available Quantities | 1 pc, 4 pcs, 10 pcs per order |
| Finish | See variant options |
| Max Deflection | See variant options |
Match the duty rating to your required spring force. Yellow (Extra Light) suits light return or ejection applications with minimal load. Blue (Light) is a step up for general-purpose tooling. Red (Medium) covers the majority of standard die and mould applications. Green (Heavy) is used where higher clamping or stripping forces are needed. Brown (Super Heavy) handles the most demanding press and forming operations. If you have a spring rate specification in N/mm, cross-reference it against the ISO 10243 table for 8mm OD springs.
The free length should be chosen so that the spring operates within its recommended deflection range — typically 20–30% of free length for light duty and up to 40–45% for heavier ratings. Measure the available pocket depth and the required working stroke, then select the shortest free length that keeps the spring within its rated deflection at maximum compression. Avoid bottoming out the spring, as this causes rapid fatigue failure.
Yes. The OD of 8mm is designed to seat in a standard 8mm counterbored pocket, and the ID of 4mm slides over a 4mm guide pin with a typical clearance fit. If your pocket or pin dimensions differ slightly, contact us to confirm compatibility before ordering.
These springs are manufactured from spring steel. Spring steel offers good mechanical properties but has limited inherent corrosion resistance. For environments with moisture, coolant exposure, or chemical contact, consider applying a light oil coating during storage and installation. If you require stainless steel die springs, please contact us to confirm availability.
Select the quantity option that matches your requirement: 1 pc for a single replacement or prototype position, 4 pcs for a small set of positions in one tool, or 10 pcs for a full die set or to maintain a workshop stock. Ordering in larger quantities reduces the per-piece cost and ensures you have spares on hand when a spring needs replacing during production.
Yes. These are mould die springs designed specifically for injection mould stripper plates, ejector return systems, and stamping/blanking die return applications. The colour-coded duty ratings align with ISO 10243 and JIS B 5012 standards commonly referenced in mould and die drawings. Confirm the required spring rate and deflection from your tooling specification before selecting a duty rating.
Mould die springs are manufactured to tighter dimensional tolerances and rated deflection specifications than general-purpose hardware springs. They are designed for cyclic loading in tooling applications where consistent spring force and fatigue life are critical. Standard hardware springs are suitable for light, non-critical applications but are not recommended as direct replacements in precision tooling.
