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When your mold or stamping die demands consistent, repeatable return force without overloading delicate tooling components, selecting the right die spring matters. Engineers, toolmakers, and hobbyist machinists working with injection molds, progressive dies, and precision fixtures need a spring that delivers controlled deflection at low load — without guesswork on sizing.
These yellow die springs feature an outer diameter (OD) of 10mm and an inner diameter (ID) of 5mm, with available free lengths ranging from 15mm to 100mm (approximately 0.59 in to 3.94 in). The yellow color coding indicates the Extra Light Load rating per ISO 10243 / JIS B 5012 standards. Each spring is wound from rectangular-section alloy steel wire for consistent coil geometry and fatigue resistance across repeated compression cycles.
Typical applications include: ejector pin return systems in plastic injection molds, blank holder springs in sheet metal stamping dies, and light-duty stripper plate assemblies in progressive tooling. Long-tail use cases also include 3D printer bed leveling mechanisms, custom jig and fixture spring returns, and small-format hydraulic press tooling where a 10mm OD die spring fits standard spring pockets.
| Spring Type | Rectangular Wire Compression Die Spring |
|---|---|
| Load Class | Extra Light Load (Yellow) |
| Standard | ISO 10243 / JIS B 5012 |
| Outer Diameter (OD) | 10 mm (0.394 in) |
| Inner Diameter (ID) | 5 mm (0.197 in) |
| Free Length Range | 15 mm – 100 mm (0.59 in – 3.94 in) |
| Wire Section | Rectangular (flat wire) |
| Material | Alloy Spring Steel |
| Surface Finish | See variant options |
| Max Deflection Rate | See variant options |
| Spring Rate | See variant options |
| End Type | Closed & Ground |
| Available Quantities | 1 pcs / 2 pcs / 5 pcs / 10 pcs |
Measure the depth of your spring pocket in the unloaded (open) position. The free length of the die spring should be equal to or slightly longer than the pocket depth to ensure the spring is pre-loaded when the tool closes. A common rule of thumb is to select a free length that allows 20–30% deflection at working load for extra light load springs.
Yellow indicates the Extra Light Load class per ISO 10243 and JIS B 5012 standards. This color-coding system allows toolmakers to instantly identify spring load ratings on the shop floor without measuring. The load classes in ascending order are: Extra Light (Yellow) → Light (Blue) → Medium (Red) → Heavy (Green) → Extra Heavy (Brown).
Extra light load die springs are designed for applications requiring low, consistent return force — such as ejector pin returns, stripper plate lifters, and light blank holders. For higher clamping or stripping forces, consider stepping up to a Blue (Light) or Red (Medium) load class spring with the same OD/ID dimensions. If you are unsure, calculate the required spring force based on your ejector plate weight and friction load before selecting a load class.
This spring has an OD of 10mm and an ID of 5mm. Your spring pocket bore should be at least 10mm in diameter (typically 10.2–10.5mm for clearance fit), and your guide pin should be no larger than 5mm in diameter. Always verify pocket diameter and guide pin size against your tooling drawings before ordering.
Yes. The extra light load rating and compact 10mm OD make these springs well-suited for 3D printer bed leveling systems, custom jig spring returns, and small fixture applications where a standard round compression spring lacks the dimensional precision of a die spring. The rectangular wire winding also provides a more consistent spring rate than typical round-wire springs of similar size.
Most small injection molds and stamping dies use 4–8 ejector return springs symmetrically arranged around the ejector plate. For prototyping or single-cavity molds, a 5-pack is usually sufficient to cover one full set plus a spare. For production tooling or multi-cavity molds, a 10-pack per spring position is recommended to have replacements on hand without reordering delays.
ISO 10243-compliant die springs are typically rated for approximately 1,000,000 cycles at the recommended working deflection (usually up to 30% of free length for extra light load). Operating beyond the rated deflection percentage significantly reduces fatigue life. For extended service life, keep working deflection within 20–25% of free length and inspect springs periodically for set (permanent length reduction) or surface cracking.
