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Finding a compression spring that holds its load rating across hundreds of cycles — without creeping, cracking, or losing free length — is a real challenge for engineers, hobbyists, and repair technicians alike. These 300mm steel compression springs are engineered for consistent axial force delivery, making them a dependable choice for anyone who needs a reliable spring in a tight space or a long-stroke assembly.
Each spring is formed from carbon steel wire with diameters ranging from 0.8mm to 4.5mm (~0.031" to ~0.177"), and outer diameters spanning 5mm to 43mm (~0.197" to ~1.693"). The free length is a fixed 300mm (~11.81"). The close-coiled helical design provides uniform pitch and consistent spring rate across the compression stroke.
Typical use cases include DIY mechanical assemblies requiring custom spring rates, industrial equipment maintenance where OEM springs are unavailable, robotics and automation jigs needing precise return-force components, and model engineering or prototype builds where exact wire-to-OD ratios matter.
| Spring Type | Compression (Helical Coil) |
|---|---|
| Free Length | 300mm (~11.81 in) |
| Wire Diameter Range | 0.8mm – 4.5mm (~0.031" – 0.177") |
| Outer Diameter Range | 5mm – 43mm (~0.197" – 1.693") |
| Material | Carbon Steel |
| Coil Direction | Right-hand (standard) |
| End Type | See variant options |
| Spring Rate | See variant options |
| Surface Finish | See variant options |
| Quantity per Order | 1 piece |
Start with your housing bore (inner diameter of the cavity the spring sits in) — the spring's OD should be 0.5mm to 1.5mm smaller than the bore for clearance. Then select a wire diameter that gives you the spring rate you need: thicker wire = stiffer spring. If you have a mandrel (inner guide rod), the spring's inner diameter (OD minus 2× wire dia.) should be at least 0.5mm larger than the mandrel.
Load capacity depends on the specific wire diameter and OD combination you select. Thicker wire diameters (e.g., 3.0mm–4.5mm) with smaller ODs produce stiffer, higher-load springs. Thinner wire (e.g., 0.8mm–1.0mm) with larger ODs produce softer, lower-load springs. Contact us to confirm load ratings for your specific variant if needed.
These springs are made from carbon steel, which offers solid mechanical strength but has limited corrosion resistance in wet or chemically aggressive environments. For outdoor, marine, or high-humidity applications, consider applying a protective coating (e.g., oil, zinc spray) after installation, or contact us to ask about alternative material options.
Yes — carbon steel compression springs can be cut to a shorter free length using a rotary tool or spring cutter. After cutting, lightly grind the end coil flat to restore a stable seating surface. Note that cutting changes the spring rate and load capacity proportionally, so recalculate your deflection requirements after trimming.
Outer diameter (OD) is the overall width of the spring coil measured from outside edge to outside edge. Inner diameter (ID) = OD minus 2× wire diameter. For example, a spring with OD 10mm and wire diameter 1.0mm has an ID of 8mm. Use OD to match your bore, and ID to match your mandrel or guide rod.
These springs are designed for general-purpose mechanical use. For high-cycle fatigue applications (millions of cycles under dynamic load), we recommend verifying the specific variant's material grade and heat treatment. Contact us to confirm suitability for your cycle count and stress requirements before ordering for critical applications.
Measure three dimensions on your existing spring: (1) Free length — the uncompressed length end-to-end; (2) Outer diameter — widest point across the coils; (3) Wire diameter — thickness of the wire itself using calipers. Match these to the variant options above. If your free length differs from 300mm, you can cut this spring to length or contact us for custom lengths.
