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When a standard spring fails under repeated cycling or heavy tooling loads, engineers and fabricators pay the price in downtime and rework. These heavy duty compression die springs are engineered for professionals, toolmakers, and serious DIYers who need reliable, consistent spring force across thousands of compression cycles without fatigue failure.
Each spring is manufactured to ISO 10243 standards in round wire coil form, available in outside diameters of 35mm (1.38 in), 40mm (1.57 in), and 50mm (1.97 in), with inside diameters of 17.5mm, 20mm, and 25mm respectively. Free lengths range from 30mm (1.18 in) up to 500mm (19.69 in) depending on the load class selected. Color-coded load ratings — Yellow (Light), Blue (Light), Red (Medium), Green (Heavy), and Brown (Heavy) — allow instant visual identification on the shop floor.
Typical use cases include stamping and punching die sets requiring consistent return force, injection mold ejector systems where spring fatigue causes costly rejects, and custom jig and fixture builds where a compression die spring for mold tooling must maintain dimensional accuracy over extended production runs. These springs are also widely used as heavy load coil springs for industrial presses and as replacement die springs for CNC machining centers.
Outside diameters of 35mm, 40mm, and 50mm with matched inside diameters, ensuring drop-in compatibility with standard die spring pockets in tooling and mold bases.
Five load ratings — Yellow (Light), Blue (Light), Red (Medium), Green (Heavy), Brown (Heavy) — color-coded for instant identification, reducing setup errors on the shop floor.
Free lengths from 30mm up to 500mm (select sizes) cover short-stroke punch returns through long-travel ejector applications without custom fabrication.
Round wire coil geometry distributes stress evenly across the coil body, extending service life under high-cycle stamping and molding conditions compared to rectangular wire alternatives at this price point.
Surface treatment provides resistance to cutting fluids, lubricants, and workshop humidity — keeping springs functional in typical metalworking and molding environments.
Each spring is sold as a single unit, so you can order exactly the OD, ID, length, and load class your application requires without paying for a full assortment pack.
| Standard | ISO 10243 |
|---|---|
| Spring Type | Compression Die Spring (Round Wire Coil) |
| Outside Diameter (OD) | 35mm / 40mm / 50mm (1.38" / 1.57" / 1.97") |
| Inside Diameter (ID) | 17.5mm / 20mm / 25mm |
| Free Length | 30mm – 500mm (see variant options) |
| Load Class / Color | Yellow – Light Load; Blue – Light Load; Red – Medium Load; Green – Heavy Load; Brown – Heavy Load |
| Material | See variant options |
| Surface Finish | See variant options |
| End Type | Closed & Ground (typical for ISO die springs) |
| Deflection Rate | See variant options |
| Operating Temperature | See variant options |
| Quantity per Order | 1 piece |
Match the OD to your die spring pocket diameter. This product offers 35mm, 40mm, and 50mm OD options. The inside diameter (17.5mm, 20mm, or 25mm respectively) must clear your guide pin with a small running clearance — typically 0.5–1mm per side. Always verify both OD and ID against your tooling drawing before ordering.
Load class indicates the spring rate and maximum load capacity at a given deflection. Yellow and Blue are Light Load — suited for light-duty ejector pins and small punch returns. Red is Medium Load — a versatile choice for general stamping dies. Green and Brown are Heavy Load — designed for high-force applications such as large-area blanking dies, heavy-duty mold ejectors, and industrial press tooling. Select based on the force your application requires at the working deflection, not just the free length.
Free length should be chosen so that the spring operates within its recommended deflection range — typically 15–30% of free length for light loads and up to 30–45% for heavy loads, depending on the ISO class. Measure your available pocket depth and required stroke, then select a free length that keeps the spring within its working deflection range. Avoid compressing die springs beyond their maximum deflection rating, as this causes rapid fatigue failure.
These springs include a surface treatment that provides resistance to common workshop fluids including water-soluble cutting oils and light lubricants. For aggressive coolant environments or high-humidity storage, periodic inspection is recommended. If your application involves prolonged immersion or highly acidic/alkaline fluids, contact us to confirm suitability.
Yes — provided the OD, ID, free length, and load class match the original specification. ISO 10243 die springs are interchangeable across manufacturers when dimensions and load class are identical. Cross-reference your existing spring's color code and dimensional markings, or measure the pocket and pin diameter directly. If you are unsure, contact us to confirm compatibility before ordering.
Service life depends on the deflection percentage used in operation. ISO 10243 die springs are typically rated for approximately 500,000 cycles at 30% deflection and 1,000,000+ cycles at 15% deflection under controlled conditions. Operating at higher deflection percentages or with misalignment will reduce service life. For critical production tooling, we recommend inspecting springs at regular intervals and replacing them proactively before failure.
Each listing is for one (1) individual spring. This allows you to order exactly the quantity, size, and load class you need. If you require larger quantities for a production tool build, simply adjust the quantity at checkout.
