Compression Spring 3.5mm Wire Dia Spring Steel Pressure/Coil Springs OD 20-50mm

Measure the bore or housing your spring will sit inside, then select an OD that provides a small clearance — typically 1–2mm smaller than the bore. For a guide rod application, measure the rod diameter and choose an inner diameter (OD minus two wire diameters) that clears the rod with 0.5–1mm of play. This product offers ODs from 20mm to 50mm to cover a wide range of fixture sizes.

Free length is the uncompressed length of the spring. Choose a free length that, when compressed to your working height, still leaves the spring above its solid height (coils fully closed). As a starting point, your working deflection should not exceed 70–80% of the free length. Available lengths here range from 60mm to 305mm to suit short-stroke and long-travel applications alike.

Spring force depends on the wire diameter, OD, free length, and number of active coils — all of which interact. With a 3.5mm wire diameter, these springs are suited for moderate-to-heavy-duty DIY and light industrial applications. For precise load requirements, use the spring rate formula (G × d⁴) / (8 × D³ × n) or contact us with your target load and deflection so we can confirm suitability.

These springs are made from spring steel, which offers good mechanical properties but has moderate corrosion resistance in dry indoor environments. For outdoor, humid, or chemically exposed applications, consider applying a light coat of corrosion-inhibiting oil or grease, or contact us to ask about surface-treated options. Avoid prolonged exposure to moisture without protection.

Yes — closed and ground ends make these springs compatible with standard flat spring seats, guide rods, and retainer cups. Verify that your guide rod diameter is smaller than the spring's inner diameter (OD minus 2× wire diameter) and that your retainer cup inner diameter is larger than the OD. With 13 OD options, you can find a match for most standard tooling.

Yes. These compression springs are commonly used in DIY 3D-printer Z-axis leveling, CNC hold-down clamps, pneumatic fixture return mechanisms, and light conveyor buffer stops. Select the OD and length that match your mounting geometry, and confirm the spring rate meets your force requirement before finalizing your design.

The pack quantity refers to the number of identical springs included in one order. Smaller packs (1 PCS) are ideal for prototyping or single-fixture builds, while 5 PCS packs offer better value for production runs or builds requiring multiple springs of the same specification. Pack availability varies by OD and length combination — check the variant selector for options.

Before ordering, confirm three dimensions: (1) OD — must clear your housing bore with 1–2mm gap; (2) inner diameter (OD − 2 × 3.5mm) — must clear your guide rod; (3) free length — must allow your required working stroke without reaching solid height. If you are unsure, order a single-piece sample of your target variant first, then scale up once fit is confirmed.