Compression Spring 3mm Wire Diameter 28-40 mm Outer Diameter Small Spring Steel

Measure the inner diameter of your spring pocket or the outer diameter of your guide rod. For a pocket-mounted spring, the OD should be 0.5–1mm smaller than the pocket bore. For a rod-guided spring, the inner diameter (OD minus 2× wire diameter, approximately OD − 6mm for these springs) should clear the rod with 0.5–1mm of radial clearance. Select from the 28mm, 29mm, 30mm, 32mm, 34mm, 35mm, 36mm, 38mm, or 40mm OD options accordingly.

Free length determines how much preload and travel your assembly can accommodate. As a starting point, your required working length (compressed length under load) plus your desired travel should not exceed the free length. Available free lengths run from 20mm to 100mm in this listing — choose the variant closest to your calculated free length, then verify the spring rate meets your load requirement.

Load capacity depends on the specific OD and free length combination you select, as each combination has a different spring rate. Spring rate (N/mm) is determined by wire diameter, OD, and number of active coils. With a 3mm wire diameter, these springs are suited for light-to-medium duty return and preload applications. For precise load data, contact us with your selected variant dimensions and we can provide further guidance.

These springs are made from spring steel, which offers good mechanical properties for most indoor and dry-environment applications. Spring steel is not inherently stainless and may show surface oxidation in humid or wet environments over time. For corrosion-sensitive applications, consider applying a light coat of machine oil or contact us about stainless steel alternatives.

Yes — 3mm wire compression springs in the 28–40mm OD range are widely used in 3D printer bed leveling, Z-axis preload, and custom automation fixtures. Verify the OD fits your spring seat, the free length provides adequate travel, and the spring rate matches your required preload force. The 2-piece pack is ideal for prototyping before committing to a 10-piece production quantity.

The 2-piece pack is best for prototyping, single-machine repairs, or testing a size before bulk ordering. The 10-piece pack offers a lower per-unit cost and is suited for production runs, maintenance stock, or projects requiring multiple identical springs. Both packs contain the same spring in the same dimensions — only the quantity differs.

Yes. Springs in series (stacked end-to-end) reduce the effective spring rate and increase total travel. Springs in parallel (side by side on the same axis) add their rates together for a stiffer combined rate. Both configurations are common in machine design. Ensure your guide rod or pocket accommodates the chosen arrangement and that the combined free length or OD fits your assembly.