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When your stamping mold, punch press, or CNC fixture demands consistent return force cycle after cycle, a weak spring is the first point of failure. Engineers and toolmakers who rely on precision machinery need a compression die spring that holds its rated load without fatigue, even under high-frequency cycling. These heavy-duty 12mm outer diameter die springs are engineered for exactly that environment.
Each spring features an outer diameter of 12mm (approx. 0.47 in) and an inner diameter of 6mm (approx. 0.24 in), with lengths ranging from 15mm to 300mm (approx. 0.59 in to 11.81 in). Available in three material grades — Alloy Steel, SWOSC-V (oil-tempered silicon-chromium wire), and 65Mn spring steel — and five load ratings: TF-Yellow (light), TL-Blue (light-medium), TM-Red (medium), TH-Green (heavy), and TB-Brown (extra-heavy).
Typical applications include injection mold return mechanisms, progressive die stamping tooling, robotic end-of-arm tooling, and precision jig and fixture assemblies. Long-tail use cases include CNC router Z-axis preload springs, hydraulic press return springs, and automation gripper compliance elements.
Consistent outer and inner diameters ensure drop-in fit on standard 6mm guide pins and into 12mm spring pockets without modification.
Choose Alloy Steel for general tooling, SWOSC-V (oil-tempered Si-Cr wire) for extended fatigue life in high-cycle applications, or 65Mn for cost-effective medium-duty use.
TF-Yellow (light), TL-Blue (light-medium), TM-Red (medium), TH-Green (heavy), and TB-Brown (extra-heavy) — color coding follows industry-standard die spring conventions for fast identification.
Available in lengths from 15mm (0.59 in) to 300mm (11.81 in), covering short-stroke punch returns to long-travel ejector pin applications.
Rectangular wire cross-section maximizes contact area and distributes stress evenly, extending service life compared to round-wire compression springs under equivalent loads.
Suited for stamping dies, injection molds, progressive tooling, robotic fixtures, CNC machines, and automation equipment requiring repeatable spring-back force.
| Outer Diameter (OD) | 12 mm (0.47 in) |
|---|---|
| Inner Diameter (ID) | 6 mm (0.24 in) |
| Free Length Range | 15 mm – 300 mm (0.59 in – 11.81 in) |
| Wire Cross-Section | Rectangular (die spring profile) |
| Material Options | Alloy Steel / SWOSC-V / 65Mn |
| Load Rating Options | TF-Yellow / TL-Blue / TM-Red / TH-Green / TB-Brown |
| Standard Reference | ISO 10243 / JIS B 5012 (die spring) |
| Surface Finish | See variant options |
| Max Deflection Rate | See variant options |
| Spring Rate | See variant options |
Select a free length that allows your required working deflection while staying within the spring's maximum deflection limit (typically 30–50% of free length for die springs). Measure the available pocket depth and the stroke of your punch or ejector pin, then add a preload allowance. If in doubt, choose a longer spring and trim the preload rather than over-deflecting a shorter one.
The color coding follows the industry-standard die spring load classification: TF-Yellow is the lightest load rating, TL-Blue is light-medium, TM-Red is medium, TH-Green is heavy, and TB-Brown is extra-heavy. Higher load ratings produce greater force at the same deflection and are suited for heavier punches, larger ejector systems, or applications requiring high return force.
Alloy Steel is the standard choice for general-purpose stamping and molding tooling. SWOSC-V (oil-tempered silicon-chromium wire) offers superior fatigue resistance and is recommended for high-cycle applications exceeding 500,000 cycles. 65Mn spring steel is a cost-effective option for medium-duty or lower-cycle tooling where budget is a priority. For critical production tooling, SWOSC-V is the preferred grade.
Yes. The 6mm inner diameter is designed to slide over standard 6mm guide pins used in ISO and JIS die sets. The 12mm outer diameter fits standard 12mm spring pockets. Always verify your specific mold or fixture dimensions before installation, as machining tolerances can vary.
Replace a die spring if you observe: (1) visible cracking or fracture, (2) a measurable reduction in free length of more than 3–5% from the original, (3) inconsistent part ejection or return force in your tooling, or (4) the spring has exceeded its rated cycle life. For SWOSC-V grade springs in high-cycle tooling, scheduled preventive replacement is recommended rather than waiting for failure.
Standard Alloy Steel and 65Mn springs are not designed for highly corrosive environments without additional surface treatment. SWOSC-V offers marginally better oxidation resistance. For applications involving coolant exposure, consider applying a rust-inhibiting coating or selecting springs with a surface treatment. For elevated-temperature applications above approximately 120°C (248°F), contact us to confirm suitability for your specific conditions.
Die springs are typically rated for a maximum working deflection of 30% of free length for heavy and extra-heavy loads, and up to 50% for lighter load ratings. Exceeding the rated deflection significantly reduces fatigue life and risks permanent set or fracture. Always design your tooling so the spring operates within its rated deflection range under maximum stroke conditions.
