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When your stamping die, CNC fixture, or automation assembly demands consistent return force without fatigue, a poorly specified spring becomes the weakest link in your build. These 6mm OD × 3mm ID mould die compression springs are engineered for makers, toolmakers, and small-batch manufacturers who need dependable elastic performance across repeated cycles — without guessing on load ratings.
Each spring features an outer diameter of 6mm (0.24 in) and an inner diameter of 3mm (0.12 in), available in lengths ranging from 15mm to 60mm (approximately 0.59 in to 2.36 in). Three color-coded load grades are offered: Yellow/TF (light load), Blue/TL (medium load), and Green/TH (heavy load), following the standard ISO 10243 mould spring color classification. Springs are wound from alloy steel wire with a consistent pitch and squared, ground ends for stable seating.
Typical use cases include die and mould return mechanisms in metal stamping and injection moulding, spring-loaded clamps and fixtures in CNC machining centers, and precision actuator return springs in robotics and automation assemblies. Long-tail applications such as "small OD compression spring for die set" and "6mm mould spring replacement" are well served by this range.
Yellow/TF = light load, Blue/TL = medium load, Green/TH = heavy load — following ISO 10243 mould spring standards for instant identification and correct specification.
6mm outer diameter and 3mm inner diameter maintained to tight tolerances, ensuring consistent fit on 3mm guide pins and in 6mm spring pockets without binding or rattle.
Available in 15, 20, 25, 30, 35, 40, 45, 50, and 60mm free lengths (0.59–2.36 in), allowing you to match the required working stroke and pre-load for your specific application.
Both ends are squared and ground flat for stable, perpendicular seating against die plates and spring pockets, minimizing lateral deflection under load.
Wound from alloy spring steel with a surface finish suited for cyclic loading in stamping and moulding environments — designed to maintain load consistency over extended service life.
Order in quantities of 1, 3, 5, 10, 15, or 25 pieces to match prototype, small-batch, or production-run requirements without over-stocking.
| Outer Diameter (OD) | 6mm (0.24 in) |
|---|---|
| Inner Diameter (ID) | 3mm (0.12 in) |
| Free Length Range | 15mm – 60mm (0.59 in – 2.36 in) |
| Load Grade / Color | Yellow/TF (Light), Blue/TL (Medium), Green/TH (Heavy) |
| End Type | Squared and ground |
| Material | Alloy spring steel |
| Surface Finish | See variant options |
| Deflection Rate | See variant options |
| Max. Deflection | See variant options |
| Pack Quantity | 1 / 3 / 5 / 10 / 15 / 25 Pcs |
| Standard Reference | ISO 10243 mould spring color classification |
Select a free length that gives you the working stroke you need plus adequate pre-load. A common rule of thumb is to compress the spring no more than 30–40% of its free length during normal operation to preserve fatigue life. For example, if your die opens 10mm, a 30mm free length spring compressed to 20mm (33% deflection) is a reasonable starting point. Measure your spring pocket depth and guide pin length to confirm fit before ordering.
These color codes follow the ISO 10243 mould spring classification system. Yellow/TF is a light-load grade suited for low-force return applications such as stripper plates in light-duty dies. Blue/TL is a medium-load grade for general-purpose die and mould work. Green/TH is a heavy-load grade for applications requiring higher force in the same physical envelope. Choose based on the return force your application requires — not just the available space.
The spring has a 6mm outer diameter and a 3mm inner diameter. It is designed to slide over a 3mm guide pin with a small clearance fit, and to seat inside a 6mm or slightly larger spring pocket. If your pocket is significantly larger than 6mm, the spring may tilt under load — consider using a guide pin or a spring retainer. Always verify your pocket diameter and guide pin diameter before installation.
These springs are made from alloy spring steel, which provides good mechanical properties for cyclic loading. Standard alloy steel springs are not inherently corrosion-resistant in wet or chemically aggressive environments. For applications exposed to coolant, moisture, or mild chemicals, consider applying a light coat of machine oil for protection, or contact us to confirm whether a coated or stainless variant is available for your requirement.
Mould die springs manufactured to ISO 10243 guidelines are typically rated for approximately 500,000 to 1,000,000 cycles when operated within the recommended deflection range (generally up to 30–40% of free length). Operating beyond the rated deflection or at excessive temperatures will reduce service life. For high-cycle production tooling, monitor springs periodically and replace as part of a planned maintenance schedule.
Yes. The compact 6mm OD makes these springs well-suited for spring-loaded locating pins, clamp return mechanisms, and actuator return springs in CNC fixtures and robotic end-of-arm tooling. Select the load grade (Yellow, Blue, or Green) based on the force required to actuate or return your mechanism, and choose a free length that provides the correct stroke within your assembly envelope.
For prototyping or single-die builds, the 1 Pcs or 3 Pcs options let you test fit and load before committing to larger quantities. For small-batch production tooling where you need spares on hand, the 10 Pcs or 15 Pcs packs offer better per-unit value. The 25 Pcs pack is suited for production environments where multiple dies or fixtures use the same spring specification and you want to minimize reorder frequency.
