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When a standard spring fails under repeated high-cycle loads, the consequences range from costly downtime to damaged tooling. Engineers, machinists, and serious DIYers who rely on stamping dies, injection molds, or custom press fixtures need a compression die spring that holds its rated load cycle after cycle without fatigue. These heavy load compression die springs are built for exactly that demand.
Each spring is manufactured to ISO 10243 heavy load (red color class) specifications, with an outer diameter (OD) ranging from 8 mm (0.31 in) to 40 mm (1.57 in), an inner diameter (ID) at approximately 50% of OD, and free lengths from 20 mm (0.79 in) up to 300 mm (11.81 in). The closed and ground ends ensure square seating and consistent load distribution across the full stroke.
Typical use cases include stamping and blanking die sets requiring controlled stripping force, injection mold ejector systems where consistent return pressure is critical, and custom mechanical assemblies such as spring-loaded clamps, fixtures, and actuators in light industrial or workshop environments.
Red-class designation confirms the highest standard load rating in the ISO die spring series, delivering maximum force per unit deflection for demanding press and mold applications.
OD from 8 mm to 40 mm paired with lengths from 20 mm to 300 mm gives you precise fitment across a broad range of die sets, fixtures, and custom assemblies without custom fabrication.
Both ends are closed and ground flat to ensure perpendicular seating, eliminating lateral drift under load and extending the service life of surrounding tooling components.
Tight pitch uniformity across the coil body maintains predictable force curves throughout the working stroke, which is essential for repeatable part quality in stamping and forming operations.
Shot-peened wire surface treatment (typical for ISO heavy load springs) reduces surface stress concentrations, supporting extended cycle life under continuous reciprocating loads.
OD / ID / free length dimensions follow ISO 10243 tables, making these springs drop-in replacements for worn or broken springs in existing tooling without re-engineering the pocket.
| Standard | ISO 10243 Heavy Load (Red) |
|---|---|
| Outer Diameter (OD) | 8 mm – 40 mm (0.31 in – 1.57 in) |
| Inner Diameter (ID) | See variant options |
| Free Length | 20 mm – 300 mm (0.79 in – 11.81 in) |
| Load Class | Heavy (Red) |
| End Type | Closed and Ground |
| Material | See variant options |
| Surface Treatment | See variant options |
| Coil Direction | Right-hand |
| Maximum Deflection | See variant options |
| Operating Temperature | Contact us to confirm |
| Quantity | 1 piece per order (select quantity at checkout) |
Measure the spring pocket diameter in your die plate — the OD of the spring should be 0.5 mm to 1 mm smaller than the pocket for clearance. For free length, select a spring whose free length is at least 1.5× your required working stroke to keep deflection within the recommended 30–35% of free length for heavy load springs. Always cross-reference with your tooling drawings or the ISO 10243 load-deflection tables.
ISO 10243 defines four load classes: light (yellow), medium (blue), heavy (red), and extra heavy (green). The heavy red class delivers approximately 50–80% more force per millimeter of deflection than the medium blue class at the same OD and free length. It is the correct choice when you need maximum stripping or ejection force in a compact spring pocket.
Standard ISO die springs are manufactured from alloy spring steel and are not inherently corrosion-resistant. For environments with coolant mist, water, or humidity, consider applying a light oil coating during storage and installation, or contact us to confirm whether a coated or stainless variant is available for your required size.
Yes. Heavy load ISO die springs are widely used in injection mold ejector plates and stripper plates. Select an OD that fits your ejector pin guide bore, and choose a free length that provides adequate return force without exceeding 30% deflection at full ejector stroke. Verify the spring rate against your required ejection force before finalizing the selection.
For heavy load (red) ISO die springs, the recommended maximum working deflection is typically 30% of the free length for extended cycle life, and up to 35% for shorter-run applications. Exceeding these limits accelerates fatigue and reduces service life. Always design your assembly so the spring operates within the recommended deflection range.
The OD selection is driven by your spring pocket size and the load requirement. Larger OD springs carry significantly higher loads — a 40 mm OD heavy spring can deliver many times the force of an 8 mm OD spring at the same deflection percentage. Start with your required stripping or ejection force, then use the ISO 10243 load tables to identify the OD and free length combination that meets your force target within the recommended deflection range.
Each order is for one (1) spring in the selected OD, ID, and length combination. If you need multiple springs for a die set, simply increase the quantity at checkout. For large-quantity requirements, contact us to discuss availability.
