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When a worn or undersized spring causes your mould to misfire, your press to bounce, or your jig to lose repeatability, the fix starts with choosing the right compression die spring. These OD 8mm / ID 4mm die springs are engineered for engineers, toolmakers, and serious DIYers who need consistent, measurable spring force — not guesswork.
Each spring features an outer diameter of 8mm and an inner diameter of 4mm, with free lengths ranging from 15mm to 100mm (approximately 0.59 in to 3.94 in). The wire is wound from high-grade spring steel with a rectangular cross-section, following the ISO 10243 colour-coding standard: Yellow (TF — Lightest Load), Blue (TL — Light Load), Red (TM — Medium Load), Green (TH — Heavy Load), and Brown (TB — Super Heavy Load). Available in packs of 1, 5, or 10 pieces.
Typical applications for these OD 8mm ID 4mm compression die springs include injection mould stripper plates, stamping and punching dies, fixture clamping systems, and precision jig return mechanisms — anywhere a compact, colour-coded spring with a known load rating is required.
Yellow (TF), Blue (TL), Red (TM), Green (TH), and Brown (TB) follow the ISO 10243 standard, making load selection fast and error-free on the shop floor.
Free lengths from 15mm to 100mm (0.59–3.94 in) cover the majority of standard mould and tooling pocket depths without custom ordering.
The flat-wire winding maximises the number of active coils within a given pocket depth, delivering higher load capacity than round-wire springs of the same envelope size.
Wound from alloy spring steel selected for fatigue resistance, these springs maintain consistent force output across repeated compression cycles in production tooling.
Order 1, 5, or 10 pieces per variant — ideal whether you need a single replacement spring or a full set for a multi-cavity mould.
OD 8mm / ID 4mm dimensions match standard die spring pocket specifications, allowing direct substitution in existing tooling without re-machining.
| Outer Diameter (OD) | 8 mm (0.315 in) |
|---|---|
| Inner Diameter (ID) | 4 mm (0.157 in) |
| Free Length Range | 15 mm – 100 mm (0.59 in – 3.94 in) |
| Wire Type | Rectangular cross-section (flat wire) |
| Material | Alloy spring steel |
| Load Rating / Colour | Yellow (TF – Lightest), Blue (TL – Light), Red (TM – Medium), Green (TH – Heavy), Brown (TB – Super Heavy) |
| Standard | ISO 10243 |
| Pack Options | 1 PCS / 5 PCS / 10 PCS |
| Finish | See variant options |
| Operating Temperature | Contact us to confirm |
Match the colour to your required spring force. Yellow (TF) is the lightest and suits delicate stripper plates or light-return mechanisms. Blue (TL) steps up for general-purpose light tooling. Red (TM) is the most common choice for standard injection moulds. Green (TH) handles heavy stamping dies, and Brown (TB) is reserved for super-heavy-duty press tooling where maximum force in a compact envelope is needed. If you have a target load value, compare it against the rated deflection force for your chosen free length.
A common rule of thumb is: Free Length = Pocket Depth + Pre-load Deflection + Working Deflection. For example, if your pocket is 40mm deep, you want 5mm of pre-load, and 10mm of working stroke, you would select a spring with a free length of approximately 55mm. Always leave at least 15–20% of the free length as solid-height clearance to avoid coil clash.
Yes. These springs are manufactured to the ISO 10243 colour-load standard, which defines OD, ID, free length, and load characteristics. An 8mm OD / 4mm ID spring will fit any pocket machined to the ISO 10243 specification for this size class. Always verify your pocket diameter and depth before installation.
These springs are made from alloy spring steel, which can be susceptible to surface rust in prolonged wet or humid conditions. For outdoor or corrosive environments, consider applying a light machine oil coating or contact us to discuss alternative finishes. For standard indoor tooling and mould applications, no additional treatment is typically required.
Measure the outer diameter (OD) and inner diameter (ID) with calipers, then measure the free (uncompressed) length. Note the colour of the original spring to identify the load rating. For this product, you are looking for OD ≈ 8mm, ID ≈ 4mm, and a free length between 15mm and 100mm. If the original spring is already compressed or deformed, measure the pocket depth and add the expected pre-load to estimate the original free length.
Rectangular (flat) wire springs pack more material into the same outer envelope compared to round-wire springs. This means they can store more energy and deliver higher load capacity for a given OD and ID. They also tend to have a more linear force-deflection curve, which is important for consistent clamping or stripping forces in precision tooling. Round-wire springs are generally lower cost but are not suitable for high-cycle or high-load die applications.
This depends on your mould design. Count the number of spring pockets in your stripper plate or ejector system. For a 4-cavity mould with 4 return springs per cavity, you would need 16 springs. The 5 PCS and 10 PCS pack options offer a lower per-unit cost and ensure you have spares on hand for maintenance. We recommend ordering at least 10–20% extra for a production mould to cover future replacements.
