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When a worn-out spring inside a pen, switch, valve, or small mechanical assembly fails, finding the right replacement in the right size is the real challenge. These small compression springs are designed for makers, repair technicians, and DIY enthusiasts who need reliable, correctly-sized springs without ordering in bulk or waiting on custom fabrication.
Each pack contains 10 pieces of carbon steel compression springs. Wire diameter options span 0.6 mm (~0.024 in), 0.7 mm (~0.028 in), and 0.8 mm (~0.031 in). Outer diameter ranges from approximately 4 mm to 13 mm (~0.16–0.51 in) depending on the selected size, and free lengths run from 5 mm to 50 mm (~0.20–1.97 in) across the full variant range.
Typical use cases include replacing springs in ballpoint pens and mechanical pencils, restoring push-button switches and latches, supporting small valve assemblies in pneumatic or hydraulic hobby projects, and providing return force in custom 3D-printed mechanisms or electronics enclosures.
| Material | Carbon Steel |
|---|---|
| Wire Diameter | 0.6 mm / 0.7 mm / 0.8 mm (see variant options) |
| Outer Diameter | 4–13 mm (see variant options) |
| Free Length | 5–50 mm (see variant options) |
| Spring Type | Compression |
| End Type | See variant options |
| Surface Finish | See variant options |
| Spring Rate | See variant options |
| Quantity per Pack | 10 pieces |
| Coil Direction | Right-hand (typical) |
Measure the bore (inner diameter of the housing) or the post (outer diameter of the guide pin) where the spring sits. The spring's outer diameter should be slightly smaller than the bore, or slightly larger than the post, to allow free movement without excessive play. Then measure the gap the spring needs to fill at rest (free length) and estimate the compressed length needed. Match these measurements to the variant options listed above.
Wire diameter directly affects spring stiffness (spring rate) and load capacity. A 0.6 mm wire produces a lighter, more flexible spring suited for low-force applications like pen mechanisms and light-duty switches. A 0.8 mm wire produces a stiffer spring with higher load capacity, better suited for latches, valves, and moderate-force return mechanisms. The 0.7 mm option sits between the two for balanced performance.
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 over extended periods. For outdoor, wet, or chemically exposed environments, consider applying a light coat of machine oil or selecting stainless steel springs instead.
These springs are well-suited for ballpoint pens, mechanical pencils, push-button switches, door latches, small valve assemblies, hobby electronics enclosures, 3D-printed mechanisms, RC model components, watch and clock repair (light-duty), and any DIY project requiring a compact compression spring with wire diameter under 1 mm.
Free length is the spring's natural, unloaded length. Measure the space available in your assembly when no force is applied — this is your target free length. Compressed length is the length the spring reaches under maximum load. Ensure the spring you select can compress to that length without coil bind (coils touching). As a conservative rule, allow at least 20–30% compression travel from free length to working length.
Carbon steel springs can develop surface rust when exposed to moisture over time. For occasional outdoor use, applying a thin layer of grease or oil will extend service life. For continuous outdoor or wet exposure, stainless steel compression springs are a more durable choice. These springs are best suited for protected indoor or enclosed mechanical assemblies.
No modification is required. Select the variant that matches your required wire diameter, outer diameter, and free length, then install directly. If you need a slightly shorter spring, compression springs can sometimes be carefully trimmed with wire cutters, but this may affect end squareness and load characteristics. Selecting the correct size from the variant list is always recommended.
