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When a project demands consistent return force in a tight space, finding a compression spring with the right wire diameter, outer diameter, and free length can be frustrating. These small stainless steel compression springs are engineered for makers, engineers, and DIY enthusiasts who need dependable elastic performance in compact assemblies — from sensor housings to pen mechanisms and miniature actuators.
Each spring is formed from stainless steel wire with a diameter of 0.4mm (approximately 0.016 in). Outer diameters span 3mm to 12mm (approx. 0.12–0.47 in), and free lengths range from 5mm to 50mm (approx. 0.20–1.97 in). The coil count and pitch vary by variant; select your combination of outer diameter and length from the options above.
Typical use cases include compression spring replacements in ballpoint pens and mechanical pencils, return-force elements in small CNC limit switches and probe assemblies, and cushioning components in lightweight robotics joints and 3D-printer extruder mechanisms.
Made from stainless steel wire, offering corrosion resistance suitable for indoor mechanical assemblies, electronics enclosures, and light-duty outdoor fixtures.
Fine 0.4mm wire gauge delivers a softer spring rate ideal for low-load applications such as contact switches, pen clips, and miniature valve returns.
Outer diameters from 3mm to 12mm and free lengths from 5mm to 50mm let you match the exact spring geometry your design requires without custom fabrication.
Available in packs of 5, 10, or 50 pieces per variant, making it easy to order just enough for prototyping or stock up for production runs.
Closed (ground or plain-closed) end coils provide flat bearing surfaces that seat squarely in spring pockets, reducing lateral deflection under load.
Suitable for CNC machine limit switches, robotics, 3D printer components, electronic device internals, hobby models, and general DIY repair projects.
| Wire Diameter | 0.4mm (approx. 0.016 in) |
|---|---|
| Outer Diameter (OD) | 3mm / 4mm / 5mm / 6mm / 7mm / 8mm / 9mm / 10mm / 12mm |
| Free Length | 5mm – 50mm (see variant options) |
| Material | Stainless Steel |
| Spring Type | Compression |
| End Type | See variant options |
| Spring Rate | See variant options |
| Surface Finish | Natural (uncoated stainless) |
| Pack Quantity | 5 pcs / 10 pcs / 50 pcs (see variant options) |
| Application | CNC, robotics, electronics, DIY repair, 3D printing |
Measure the inner diameter of the bore or spring pocket where the spring will sit. The spring's outer diameter should be slightly smaller than the bore — typically 0.2–0.5mm clearance — to allow free compression without binding. For a shaft-guided spring, the inner diameter of the spring (OD minus 2× wire diameter) should be slightly larger than the shaft.
The free length is the uncompressed length of the spring. Choose a free length that is longer than your required working length. The difference between free length and working length determines how much force the spring exerts. For light-duty applications such as pen mechanisms or contact switches, a free length 1.5–2× the working length is a common starting point.
With a 0.4mm wire diameter, these are light-duty springs suited for low-load applications. Exact spring rates vary by outer diameter and free length (see variant options). They are not intended for heavy mechanical loads. Typical uses include return forces in switches, pen clips, and small actuators where forces are measured in grams to low Newtons.
Yes. Stainless steel provides good corrosion resistance for indoor environments, electronics enclosures, and light-duty outdoor use. For highly corrosive environments (salt spray, strong acids/bases), additional protective measures or a different alloy may be required. Contact us to confirm suitability for your specific environment.
These springs are designed to standard coil geometry and should fit most spring seats and plunger bores sized for the corresponding outer diameter. Always verify the bore diameter, shaft diameter (if shaft-guided), and seating depth against the spring dimensions before ordering. Refer to the variant options for exact OD and length combinations.
Yes. These small compression springs are commonly used in 3D printer extruder assemblies, bed-leveling mechanisms, and CNC limit switch returns. Select the OD and free length that matches your printer or machine's spring pocket dimensions. The 0.4mm wire diameter provides a soft spring rate appropriate for these light-duty precision applications.
If you are prototyping or need springs for a single repair, the 5-piece or 10-piece pack is the most economical choice. If you are building a batch of assemblies, running a production run, or want spares on hand, the 50-piece pack offers a lower per-unit cost. Both packs contain identical springs — only the quantity differs.
