Bronze is the sliding-bearing material: it conforms to a misaligned shaft, embeds grit instead of denting, tolerates marginal lubrication, and survives seawater. It is not a substitute for a rolling bearing under high load.
| Designations | CuSn6 · C93200 (SAE 660) · CuSn8 · phosphor bronze · gunmetal (CuSn10Zn2) |
|---|---|
| Hardness | HB 65–90 depending on alloy |
| Density | 8.80 g/cm³ |
| Max service temperature | ≈250 °C (with appropriate lubricant) |
| Corrosion resistance | Good — seawater, most industrial fluids; not for ammonia |
| Load capacity | High for a sliding bearing, but far below a rolling bearing |
| Friction | 0.08–0.15 lubricated against steel |
| Relative cost | ≈2× 52100 for an equivalent size |
Bronze bushings work by being softer than the shaft. When debris enters, the bronze embeds it rather than letting it score the shaft. When the shaft is misaligned, the bronze wears in and conforms. When lubrication is intermittent, the bronze surface holds a film and, in oil-impregnated grades, supplies its own. These are properties a hardened steel rolling bearing does not have.
The trade-off is efficiency. A bronze bushing is a sliding contact: friction is much higher than rolling, so it runs hotter and consumes more energy. Above a certain speed and load, the heat generated exceeds what the bearing can shed, and a rolling bearing becomes the only workable choice.
Below roughly 1–2 m/s sliding velocity and moderate load, bronze is simple, robust and cheap to maintain. Above that, friction heat rises with velocity and the bushing either wears fast or demands a pressure-fed oil system. A rolling bearing handles far higher speed at far lower friction, but demands a hard, ground, aligned shaft and clean lubrication — which is exactly what a bronze bushing does not need.
| Property | Cast bronze bushing | Deep groove ball bearing (52100) | PTFE-lined plain bearing |
|---|---|---|---|
| Friction | 0.08–0.15 lubricated | 0.001–0.003 | 0.04–0.10 |
| Speed limit | Low (≈1–2 m/s sliding) | High | Low |
| Shaft requirement | Soft is fine, worn is fine | Hard (≥58 HRC) and ground | Hard and smooth |
| Debris tolerance | Excellent — embeds | Poor — dents and spalls | Good |
| Misalignment tolerance | Good | Limited (unless self-aligning) | Good |
| Seawater | Good | Poor | Good |
Steel-on-bronze and bronze-lined rod ends.
Read →Cast housings often paired with bronze or polymer bushings.
Read →Shock, dirt and misalignment — bronze's home ground.
Read →When lubrication must be eliminated entirely.
Read →Only if the shaft can be reworked and the speed is low. A ball bearing needs a hardened, ground, aligned shaft; a bronze bushing does not. Swapping the other way — ball bearing to bronze — usually requires reducing speed.
Yes. Bronze is one of the traditional seawater bearing materials for rudder stocks, stern tubes (with appropriate sleeve materials) and deck machinery. It is not immune to erosion or to galvanic effects with steel, so the pairing matters.
A sintered bronze bushing with 15–25% porosity, vacuum-impregnated with oil. It supplies its own lubricant for long periods, which suits intermittent, low-speed duty such as domestic equipment and light machinery.
Edge loading from misalignment, or a shaft that deflects under load. Bronze conforms and wears in, but if the misalignment is large or the load is one-sided, wear concentrates. Self-aligning or spherical plain designs solve it.
| Industry | Duty | Where it fits | |
|---|---|---|---|
| Pumps & Compressors | continuous running, thrust reversal and process fluid along the shaft | Slurry & dirty service | Detail → |
| Machine Tools & Spindles | speed, stiffness and thermal growth of the spindle | Screw support & ways | Detail → |
| Conveyors & Bulk Handling | slow speed, abrasive dust and frame misalignment | Slow, heavy pulley shafts | Detail → |
| Mining & Aggregate | shock, abrasion and water sprays with little maintenance access | Crusher bushes | Detail → |
| Steel & Metallurgy | very high load, heat and cooling water washing the grease out | Mill auxiliaries | Detail → |
| Wind Turbines | very long life, oscillating pitch and yaw motion, moisture ingress | Yaw & pitch sliding | Detail → |
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