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When a mechanism fails because a tiny spring loses tension or snaps under repeated cycling, the whole assembly stops. Engineers, hobbyists, and repair technicians who work with compact electronics, precision instruments, or small mechanical assemblies know how hard it is to source the exact wire diameter and free length they need. These small compression springs are stocked in a wide matrix of wire diameters and outer diameters so you can match the spec without compromise.
Each pack contains 10 pieces of compression spring made from carbon steel wire. Wire diameter ranges from 0.3 mm to 0.5 mm (approximately 0.012 in to 0.020 in); outer diameter spans 2 mm to 10 mm (approximately 0.079 in to 0.394 in); free length options run from 5 mm to 50 mm (approximately 0.197 in to 1.969 in). The spring body is wound with consistent pitch and squared ends to allow stable seating.
Typical use cases include pen and stylus click mechanisms requiring a small compression spring for retraction, sensor and switch assemblies in consumer electronics needing a miniature steel spring for contact force, and DIY model-making or robotics projects where a precision compression spring in the 2–10 mm OD range provides controlled return force without adding bulk.
Wire dia. 0.3–0.5 mm × OD 2–10 mm × lengths 5–50 mm — over 200 size combinations to match your exact spec.
Wound from carbon steel wire for consistent elastic modulus and reliable return force across repeated compression cycles.
Flat-seated ends ensure stable axial alignment in bores, pockets, and plunger housings without tilting under load.
Uniform coil spacing maintains linear force-deflection behavior, making these springs predictable in precision mechanisms.
Enough quantity for prototyping, repair stock, or small-batch production without over-ordering bulk reels.
Designed for tight-clearance assemblies — pen mechanisms, micro-switches, sensor contacts, and small robotics joints.
| Material | Carbon Steel |
|---|---|
| Wire Diameter | 0.3 mm / 0.4 mm / 0.5 mm (see variant options) |
| Outer Diameter (OD) | 2 mm – 10 mm (see variant options) |
| Free Length | 5 mm – 50 mm (see variant options) |
| End Type | Squared (closed) ends |
| Winding Direction | Right-hand |
| Spring Type | Compression |
| Quantity per Pack | 10 pieces |
| Surface Finish | See variant options |
| Spring Rate | See variant options |
Match three dimensions: outer diameter (OD) to your bore or pocket diameter, wire diameter to your required load capacity, and free length to your travel plus compressed height. For light-duty applications such as pen mechanisms or micro-switches, wire diameters of 0.3–0.4 mm with OD 2–5 mm are typical. For slightly higher loads in small robotics or sensor assemblies, 0.5 mm wire with OD 5–10 mm is a common choice. Select your exact combination from the variant options above.
Due to the small wire diameters (0.3–0.5 mm), these springs are designed for light-duty applications. Typical spring rates and maximum loads vary by size combination. They are suited for contact-force applications in electronics, pen retraction mechanisms, and small sensor assemblies — not for structural or heavy-load use. If you need specific spring rate data for your size, contact us to confirm.
These springs are made from carbon steel, which provides good mechanical properties but has limited corrosion resistance compared to stainless steel. For indoor, dry, or low-humidity environments they perform reliably. If your application involves moisture, chemicals, or outdoor exposure, consider applying a light protective coating or contact us about alternative material options.
Many ballpoint pen and stylus retraction mechanisms use springs in the 0.3–0.4 mm wire diameter range with OD 2–4 mm and free lengths of 10–25 mm. Select the variant that matches your existing spring's dimensions. If you are unsure, measure the OD, wire diameter, and free length of the spring you are replacing and match accordingly from the size options above.
Yes. These miniature compression springs are commonly used as contact springs in battery compartments, switch plungers, and sensor housings on PCBs. Ensure the OD fits within your component footprint and the free length provides the correct preload for your contact force requirement. For applications requiring electrical conductivity through the spring, verify contact resistance is acceptable for your circuit.
Use a digital caliper to measure: (1) Outer Diameter — measure across the outside of the coils. (2) Wire Diameter — measure the thickness of the wire itself. (3) Free Length — measure the spring at rest, uncompressed. Match all three values to the variant options listed above. A slight tolerance of ±0.05 mm on wire diameter and ±0.1 mm on OD is generally acceptable for most replacement applications.
Wire diameter directly affects spring stiffness (spring rate) and load capacity. A 0.3 mm wire spring is the lightest and most flexible — ideal for very low-force applications like pen clicks or micro-contacts. A 0.4 mm wire spring offers a moderate spring rate suitable for small switches and light mechanical returns. A 0.5 mm wire spring is the stiffest of the three, providing more force per unit of deflection, making it appropriate for slightly heavier contact or return-force requirements in small assemblies.
