5pcs Wire Dia. 3.0-3.5 mm OD 18mm-40mm Small Springs Compression Spring Steel

Measure the bore or housing your spring sits inside. The spring's outer diameter should be slightly smaller than the bore to allow free movement without binding. For a spring that fits over a rod or pin, the inner diameter (OD minus twice the wire diameter) must be larger than the rod diameter. Select your OD from the variant dropdown and verify clearances before ordering.

A thicker wire diameter (3.5mm) produces a stiffer spring with a higher spring rate, meaning it resists compression more strongly. A 3.0mm wire diameter yields a softer spring with more travel for the same load. If you are replacing an existing spring, match the wire diameter of the original. If designing from scratch, use a spring rate calculator with your load and deflection requirements to determine the appropriate wire size.

These springs are made from carbon steel, which offers moderate corrosion resistance in dry indoor environments. For outdoor, humid, or chemically exposed applications, consider applying a light coat of machine oil or grease, or look for stainless steel spring variants. Carbon steel springs are best suited for protected mechanical assemblies, jigs, fixtures, and indoor tooling.

Yes. Compression springs can be stacked in series (end-to-end) to increase total travel while maintaining the same spring rate, or in parallel (side-by-side) to increase the combined spring rate. Ensure the spring seats and housing geometry accommodate the configuration. Each pack contains 5 pieces, making it convenient to set up multi-spring assemblies.

Free length is the overall length of the spring when no load is applied. It determines how much compression travel (deflection) is available before the spring reaches solid height. Choose a free length that gives you adequate working deflection for your application — typically the free length should be 20–30% longer than the compressed working length to avoid coil bind.

Check three dimensions against your assembly: (1) Outer diameter vs. bore clearance, (2) Inner diameter vs. guide rod diameter, and (3) Free length vs. available cavity depth. All three dimensions are specified in the variant selector. If you need to confirm spring rate or solid height for a specific variant, contact us before ordering.

These springs are designed for general-purpose mechanical use in DIY, maintenance, and light industrial applications. For high-cycle fatigue environments (millions of cycles under dynamic load), consult a spring engineer and consider springs manufactured to specific fatigue standards. For typical workshop, fixture, and repair use cases, these springs provide reliable performance.