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When a mechanism fails because a spring loses tension too quickly or collapses under load, the root cause is usually a mismatch between wire diameter and coil geometry. Engineers, maintenance technicians, and hands-on DIYers who need a reliable, long-travel compression spring in a 300 mm free length will find this range covers the most common industrial and workshop demands without requiring custom fabrication.
Each spring in this series is wound from round steel wire with a diameter of 2.5 mm to 4.5 mm (0.098"–0.177") and an outer diameter ranging from approximately 14 mm to 43 mm (0.55"–1.69"). The free length is a uniform 300 mm (11.81"). End coils are closed and ground flat to provide stable seating and even load distribution across the full compression stroke.
Typical applications include industrial machinery damping and return mechanisms, automotive suspension jigs and test fixtures, gate and door return assemblies, and custom DIY fabrication projects where a 300 mm compression spring with a defined wire gauge is required. The broad wire-diameter selection also makes these springs suitable for spring-loaded clamps, pneumatic valve returns, and light-duty press tooling.
| Free Length | 300 mm (11.81") |
|---|---|
| Wire Diameter | 2.5 mm – 4.5 mm (0.098" – 0.177") |
| Outer Diameter (OD) | See variant options |
| End Type | Closed and ground |
| Spring Rate | See variant options |
| Material | Steel (carbon spring steel) |
| Finish / Coating | See variant options |
| Coil Direction | Right-hand |
| Load Type | Compression |
| Weight | See variant options |
Wire diameter directly determines the spring rate and load capacity. Lighter wire gauges (2.5–3.0 mm) are suited for return mechanisms, light damping, and low-load applications. Heavier gauges (3.5–4.5 mm) handle higher compressive loads and are better for structural or load-bearing assemblies. If you know your required load at a specific deflection, use Hooke's Law (F = k × x) with the spring rate for your chosen variant to confirm suitability.
For a spring operating inside a bore, the OD should be 1–2 mm smaller than the bore diameter to allow free movement without binding. For a spring operating over a rod or guide pin, the inner diameter (ID = OD minus twice the wire diameter) should be 1–2 mm larger than the rod diameter. Check the variant name for the OD, then calculate ID accordingly before ordering.
These springs are manufactured from carbon spring steel. Carbon steel offers good mechanical properties for dry or lightly oiled indoor environments. For applications exposed to moisture, chemicals, or outdoor conditions, consider applying a protective coating (such as grease or a corrosion-inhibiting spray) after installation, or contact us to confirm whether a coated variant is available for your size.
Uncoated carbon steel springs are not recommended for prolonged outdoor or wet exposure without additional protection. If your application involves moisture or humidity, apply a rust-inhibiting lubricant regularly, or enquire about stainless steel alternatives. For occasional outdoor use in sheltered conditions, a light coating of grease at installation will extend service life significantly.
The solid height is reached when all coils are fully compressed and touching. Operating a spring at or near solid height repeatedly causes set (permanent deformation) and reduces fatigue life. As a general guideline, limit working deflection to no more than 70–80% of the available travel (free length minus solid height). The exact solid height depends on the number of active coils and wire diameter of your chosen variant — contact us if you need this data for a specific size.
Each listing is for a single spring (qty 1). If you need multiple springs for a project, simply adjust the quantity in your cart. Bulk pricing may be available for larger orders — contact us through the store for volume enquiries.
Spring rate depends on wire diameter, OD, and number of active coils. If you require precise spring rate or load-at-deflection data for a specific size in this range, please contact us with the variant name (e.g., "3.0 x 25 x 300 mm") and we will provide the technical data sheet for that spring.
