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When your project demands consistent, repeatable spring force in a compact form factor, undersized or mismatched springs cause costly failures. Whether you are a hobbyist assembling electronics, a maker building mechanical linkages, or a technician repairing small devices, finding the right compression spring in the right size is often the hardest part. These 0.4mm wire diameter compression springs are stocked in a wide range of outer diameters and free lengths so you can match your exact application without compromise.
Each spring is formed from carbon steel wire with a 0.4mm (approximately 0.016 in) diameter. Outer diameters span 3mm to 10mm (approximately 0.12 in to 0.39 in), and free lengths range from 5mm to 50mm (approximately 0.20 in to 1.97 in). Springs are available in packs of 10, 50, or 100 pieces to suit both prototyping and small-batch production needs.
Typical use cases include compression spring replacements in pen mechanisms and clicker buttons, return springs in miniature switches and relays, preload springs in optical assemblies and camera modules, and cushioning elements in small consumer electronics. The consistent coil pitch and uniform wire diameter make these springs well-suited for any application requiring repeatable compression spring force in a small pressure spring format.
Consistent wire gauge across all variants ensures uniform spring rate and predictable deflection behavior in precision assemblies.
Eight outer diameter options from 3mm to 10mm (0.12–0.39 in) let you match standard bore sizes without custom fabrication.
Ten length options from 5mm to 50mm (0.20–1.97 in) cover a broad range of travel and preload requirements in a single product listing.
Choose 10, 50, or 100 pieces per order — ideal for prototyping, repair stock, or small-batch production runs.
Standard closed-coil end treatment provides a flat seating surface for stable load transfer and consistent spring alignment in housings.
Used in pen mechanisms, miniature switches, relay return springs, optical preload assemblies, and small consumer electronics repair.
| Wire Diameter | 0.4mm (approx. 0.016 in) |
|---|---|
| Outer Diameter Range | 3mm – 10mm (approx. 0.12 – 0.39 in) |
| Free Length Range | 5mm – 50mm (approx. 0.20 – 1.97 in) |
| Material | Carbon Steel |
| Surface Finish | See variant options |
| Spring Rate | See variant options |
| End Type | Closed (typical) |
| Pack Quantity | 10 pcs / 50 pcs / 100 pcs |
| Coil Direction | Right-hand (typical) |
| Load Capacity | See variant options |
Measure the bore or housing your spring will sit inside. The spring's outer diameter should be slightly smaller than the bore — typically 0.2–0.5mm clearance — to allow free movement without binding. For a shaft-guided spring, the inner diameter (OD minus twice the wire diameter) should be slightly larger than the shaft.
Free length is the uncompressed length of the spring. Select a free length longer than your required working length. The difference between free length and working length is the compression travel. Ensure the spring does not reach solid height (coil bind) at maximum compression in your assembly.
With a 0.4mm wire diameter, these are light-duty compression springs suited for low-force applications such as button return mechanisms, contact preloads, and small device assemblies. They are not intended for heavy industrial or high-load structural applications. If you need a specific spring rate or load value, please contact us to confirm before ordering.
These springs are made from carbon steel, which offers good mechanical properties but limited corrosion resistance in humid or wet environments. For outdoor or moisture-exposed applications, consider applying a light coating of oil or grease, or contact us about stainless steel alternatives.
Yes. The small OD range (3–10mm) and short length options (5–15mm) make these springs well-suited for use as contact springs, battery terminal springs, and button return springs in PCB and electronics assemblies. Verify the spring rate and travel match your design tolerances.
All three quantity options contain identical springs — only the pack count differs. The 10pcs option is ideal for prototyping or single repairs. The 50pcs and 100pcs options offer a lower per-unit cost and are suited for small-batch production, maintenance stock, or projects requiring multiple springs of the same specification.
We recommend ordering the 10pcs pack first to verify fit, travel, and load in your application. Once confirmed, you can order the 50pcs or 100pcs pack for your production or stock needs.
