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When a failed spring brings a project to a halt, finding the exact wire diameter and outer diameter combination matters. These black compression springs are designed for hobbyists, makers, engineers, and repair technicians who need reliable, consistent spring force across a wide range of compact and mid-size assemblies.
Each spring is formed from steel wire and finished with a black surface treatment. Wire diameters span 0.3 mm to 6 mm (~0.012"–0.236"), outer diameters range from 3 mm to 50 mm (~0.118"–1.969"), and all variants share a uniform free length of 305 mm (~12.0"). End coils are closed and ground for stable seating on flat surfaces.
Typical use cases include compression spring replacement for mechanical assemblies, small compression spring for electronics enclosures and PCB fixtures, and steel coil spring for automotive, robotics, and industrial tooling prototypes where consistent load deflection is required.
Wire diameters from 0.3 mm to 6 mm paired with outer diameters from 3 mm to 50 mm — one listing covers light-duty to heavy-duty spring requirements.
All variants share a 305 mm (~12.0") free length, making it straightforward to cut-to-length or use as-is for longer travel applications.
The black coating provides a layer of surface protection and a clean appearance suitable for visible assemblies and finished products.
Closed and ground end coils ensure flat, stable seating against spring seats and guide rods, reducing lateral deflection under load.
Steel wire provides reliable elastic return and consistent spring rate across repeated compression cycles in mechanical and DIY applications.
Suited for electronics fixtures, robotics, automotive components, tooling jigs, and general mechanical assemblies requiring controlled compression force.
| Material | Steel |
|---|---|
| Surface Finish | Black |
| Wire Diameter Range | 0.3 mm – 6 mm (0.012" – 0.236") |
| Outer Diameter Range | 3 mm – 50 mm (0.118" – 1.969") |
| Free Length | 305 mm (12.0") |
| End Type | Closed and Ground |
| Spring Type | Compression |
| Spring Rate | See variant options |
| Max Load Capacity | See variant options |
| Weight | See variant options |
Match the outer diameter to your bore or housing inner diameter (leave ~0.5–1 mm clearance), and select the wire diameter based on the load you need to support — thicker wire = higher spring rate. If you are replacing an existing spring, measure the old spring's wire diameter, outer diameter, and free length directly.
Spring rate varies by wire diameter and outer diameter combination. Larger wire diameters and smaller outer diameters generally produce stiffer springs. Refer to the variant options or contact us for specific spring rate data on your chosen size.
The black surface finish provides a degree of surface protection against light moisture and oxidation. For applications exposed to prolonged moisture, chemicals, or outdoor environments, consider additional protective coatings or stainless steel alternatives.
Yes. Steel compression springs can be cut to a shorter free length using a rotary cutting tool or spring cutter. Note that cutting changes the spring rate and end condition — grind the cut end flat for stable seating after cutting.
These springs are compatible with a wide range of applications including electronics enclosures, robotics actuators, automotive components, tooling jigs, 3D printer extruder assemblies, door latches, and general mechanical prototypes. Verify the outer diameter fits your bore and the wire diameter provides the required load.
Measure your existing spring or housing: (1) inner bore diameter — select an outer diameter ~0.5–1 mm smaller; (2) guide rod diameter — select an inner diameter (outer diameter minus 2× wire diameter) larger than the rod; (3) required free length — 305 mm can be used as-is or cut down. Contact us if you need help selecting the right variant.
These springs are suited for general-purpose and moderate-cycle applications. For high-cycle fatigue environments (millions of cycles), consult us for material and heat-treatment specifications to confirm suitability for your load and deflection requirements.
