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When a standard spring is too large for your project, finding a reliable miniature compression spring becomes a real challenge. Whether you are a hobbyist repairing a mechanical pen, an engineer prototyping a sensor housing, or a maker building a custom switch mechanism, these small-diameter steel compression springs give you the exact elastic force you need in a compact form factor.
Each spring is wound from carbon steel wire with a diameter of 0.3 mm, 0.4 mm, or 0.5 mm (approximately 0.012–0.020 in). The outer diameter ranges from 3 mm to 10 mm (approximately 0.12–0.39 in), and free lengths span from 5 mm to 100 mm (approximately 0.20–3.94 in) depending on the variant selected. Springs are sold in packs of 5 or 10 pieces per order.
These miniature compression springs are well suited for small electronics repair and PCB spring contacts, precision mechanical models and scale assemblies, and custom jig or fixture designs requiring consistent return force in a confined space.
| Material | Carbon steel |
|---|---|
| Wire Diameter | 0.3 mm / 0.4 mm / 0.5 mm (approx. 0.012–0.020 in) |
| Outer Diameter (OD) | 2 mm – 10 mm (approx. 0.08–0.39 in) — see variant options |
| Free Length | 5 mm – 100 mm (approx. 0.20–3.94 in) — see variant options |
| Spring Type | Compression (closed ends) |
| Coil Direction | Right-hand wound |
| Surface Finish | See variant options |
| Spring Rate | See variant options |
| Pack Quantity | 5 Pcs (lengths ≥60 mm) / 10 Pcs (lengths ≤50 mm) |
| Weight (per pack) | See variant options |
Measure the inner diameter of the bore or pocket where the spring will sit. The spring's outer diameter should be 0.1–0.3 mm smaller than the bore to allow free movement without binding. For a shaft-guided spring, the inner diameter of the spring (OD minus twice the wire diameter) should be 0.1–0.3 mm larger than the shaft.
A thicker wire diameter produces a stiffer spring with a higher spring rate, meaning more force is required to compress it by the same distance. Choose 0.3 mm wire for very light loads and delicate mechanisms, 0.4 mm for moderate loads, and 0.5 mm when you need a firmer return force in the same outer diameter envelope.
These springs are made from carbon steel, which offers good mechanical properties but limited corrosion resistance compared to stainless steel. For indoor, dry, or low-humidity environments they perform reliably. For outdoor, wet, or chemically exposed environments, consider applying a light coat of oil or selecting a stainless steel alternative.
The free length is the uncompressed length of the spring. Select a free length that is longer than your required working length by at least 20–30% to ensure the spring operates within its elastic range and does not reach solid height (coil bind) during normal use. For example, if your mechanism compresses the spring by 10 mm, choose a free length of at least 13–15 mm.
Yes. The small wire diameters (0.3–0.5 mm) and outer diameters (as small as 2–3 mm) make these springs suitable for spring-loaded PCB contacts, battery terminals, push-button mechanisms, and similar low-load electronic applications. Ensure the spring material is compatible with any soldering or conformal coating processes in your assembly.
Shorter springs (5–50 mm free length) are sold in packs of 10, which is ideal for prototyping or small batch production where you need spares. Longer springs (60–100 mm free length) are sold in packs of 5. If you need a larger quantity for production runs, simply add multiple units to your cart.
The inner diameter equals the outer diameter minus twice the wire diameter. For example, a spring with OD 5 mm and wire diameter 0.5 mm has an inner diameter of approximately 4 mm (5 mm − 2 × 0.5 mm). Use this formula to verify shaft clearance before ordering.
