Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
When a standard spring fails under load or corrodes after a season outdoors, the whole assembly suffers. Engineers, machinists, and serious DIYers who need reliable black compression springs turn to a solution that holds its rate under repeated cycling without visible rust creep. These black oxide compression springs are built for exactly that — consistent force delivery in demanding environments where a flimsy spring is not an option.
Each spring is formed from spring steel wire with diameters ranging from Ø1.5 mm to Ø6 mm (approx. 0.059 in to 0.236 in). Outer diameters span 8 mm to 50 mm (approx. 0.31 in to 1.97 in), and free lengths run from 110 mm to 400 mm (approx. 4.3 in to 15.7 in). The black oxide surface treatment provides a uniform matte finish that reduces surface friction and offers a baseline level of corrosion inhibition compared to bare steel.
Typical use cases include industrial machinery return mechanisms, automotive suspension jigs and fixture clamps, heavy-duty drawer and cabinet hardware, robotic actuator assemblies, and custom DIY press or tensioning rigs where a specific spring rate and free length must be matched precisely.
| Material | Carbon Spring Steel |
|---|---|
| Surface Finish | Black Oxide |
| Wire Diameter | Ø1.5 mm – Ø6 mm (0.059 in – 0.236 in) |
| Outer Diameter (OD) | 8 mm – 50 mm (0.31 in – 1.97 in) |
| Free Length | 110 mm – 400 mm (4.3 in – 15.7 in) |
| End Type | See variant options |
| Spring Rate | See variant options |
| Load Capacity | See variant options |
| Quantity per Pack | 1 piece per variant |
| Coil Direction | Right-hand (standard) |
Start with the bore or housing diameter your spring must fit inside — the spring OD should be 0.5–1 mm smaller than the bore for clearance. Then select a wire diameter that delivers the spring rate you need: thicker wire (e.g. Ø4–6 mm) produces a stiffer spring, while thinner wire (e.g. Ø1.5–2 mm) gives a softer rate. Use the variant selector above to match both dimensions to your design.
These springs are formed from carbon spring steel, which is engineered for elastic deformation — meaning the coils return to their original free length after each compression cycle. Fatigue life depends on the deflection ratio (how far you compress relative to free length); keeping deflection below 80% of the solid height significantly extends service life in high-cycle applications.
Black oxide provides a baseline level of corrosion inhibition compared to bare steel by converting the surface layer to magnetite. It is not equivalent to zinc plating or stainless steel in wet or salt-spray environments. For outdoor or high-humidity use, we recommend applying a light coat of oil or grease after installation to extend service life.
Yes — the inner diameter (ID) of each spring is approximately OD minus twice the wire diameter. For example, a spring with OD 25 mm and wire Ø2 mm has an ID of roughly 21 mm. Ensure your guide rod diameter is at least 0.5 mm smaller than the ID to allow free travel without binding. Check the variant dimensions before ordering.
Yes. These black compression springs are commonly used in automotive jig fixtures, press tooling, valve return mechanisms, and industrial machinery where a specific free length and OD must be matched. Always verify the spring rate and solid height against your load and travel requirements before installation in safety-critical assemblies.
The length listed is the free length — the uncompressed length of the spring. Choose a free length that gives you adequate travel (compression distance) for your application. A longer free length allows more total deflection before reaching solid height. Select the length that fits your housing depth and required stroke in the variant selector above.
Spring rate (k) = Load (N) ÷ Deflection (mm). If you need to support 50 N over 10 mm of travel, you need a spring rate of 5 N/mm. Spring rate increases with wire diameter and decreases with more active coils or a larger OD. If you need help matching a specific rate, contact us with your load and travel requirements.
