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When a project demands consistent push-back force and your existing spring has lost tension or snapped under load, finding the right replacement quickly matters. These black compression springs are designed for hobbyists, makers, and maintenance professionals who need a dependable stock of mechanical springs across a wide range of sizes — without waiting on custom orders.
Each spring is wound from carbon steel wire with a black surface finish (typically phosphate-coated or painted for corrosion inhibition). Wire diameters are 3mm and 6mm, with outer diameters ranging from approximately 16mm to 47mm (0.63–1.85 in) and free lengths from 30mm to 355mm (1.18–13.98 in). Sold in packs of 1, 2, or 5 pieces depending on the variant selected.
Typical use cases include DIY mechanical assemblies requiring return-force springs, small machine maintenance and repair (replacing worn compression springs in jigs, fixtures, or tooling), and hobbyist robotics or automation projects where consistent spring rates in compact coil springs are needed.
| Material | Carbon steel |
|---|---|
| Surface Finish | Black (phosphate or painted) |
| Wire Diameter | 3mm / 6mm (see variant options) |
| Outer Diameter | See variant options (16–47mm / 0.63–1.85 in) |
| Free Length | See variant options (30–355mm / 1.18–13.98 in) |
| Spring Type | Compression (coil) |
| End Type | Closed and ground (typical) |
| Spring Rate | See variant options |
| Pack Quantity | 1 / 2 / 5 pcs (see variant options) |
| Application | General mechanical, DIY, light industrial |
Measure the bore or housing your spring sits in to determine the maximum outer diameter. Measure the gap the spring must fill at rest (free length) and the compressed height you need. Select a variant whose outer diameter fits inside the bore with a small clearance (typically 1–2mm) and whose free length matches your assembly requirements.
Wire diameter directly affects spring stiffness (spring rate) and load capacity. The 6mm wire diameter springs are significantly stiffer and suited for heavier loads, while the 3mm wire diameter springs are better for lighter-duty return-force applications. Always match wire diameter to your required load and deflection specifications.
The black surface finish provides light surface protection against oxidation, but these are carbon steel springs and are not rated for prolonged exposure to moisture, salt spray, or harsh chemicals. For outdoor or wet environments, consider stainless steel springs. These are best suited for indoor mechanical assemblies and protected enclosures.
Closed ends mean the last coil is wound tightly against the adjacent coil, and ground ends mean the tip is machined flat. This creates a stable, flat seating surface so the spring sits squarely against its mounting surface without tilting, which is important for consistent, predictable compression force.
Standard carbon steel compression springs are generally suitable for ambient temperatures up to approximately 120°C (248°F). For higher-temperature applications, specialized alloy or stainless steel springs are recommended. Contact us to confirm suitability for your specific operating conditions.
If you need a single replacement for a broken spring, the 1-piece option is the most economical. For small project builds where you need a spare, 2 pieces is a practical choice. The 5-piece pack offers the best per-unit value and is ideal if you are building multiple assemblies or want to keep spares on hand for future maintenance.
Use a caliper to measure: (1) wire diameter — the thickness of the wire itself; (2) outer diameter — the widest point of the coil; (3) free length — the total length of the spring when uncompressed. Match all three measurements to the variant options listed above. If your spring is slightly worn or deformed, measure the housing dimensions as a cross-reference.
