Copper
The Foundation of Bearing Alloys
Copper is the essential base element for bronze, brass, and other bearing alloys. Its unique combination of thermal conductivity, corrosion resistance, and alloying versatility makes it indispensable in bearing technology.
Copper in Bearing Applications
Copper (Cu) has been used in bearing applications for thousands of years. While pure copper is rarely used directly as a bearing surface due to its softness and tendency to gall, it serves as the base element for the world's most important bearing alloys — bronze and brass.
When alloyed with tin, copper becomes bronze — the classic bearing material prized for its wear resistance and load capacity. When alloyed with zinc, it becomes brass — offering excellent machinability and corrosion resistance. These copper-based alloys form the backbone of industrial bearing technology.
JBM manufactures bearings from a wide range of copper alloys, from cast bronze bushings to wrapped phosphor bronze bearings. Understanding copper's properties helps you select the right alloy for your application.
Copper-Based Bearing Alloys
Tin bronze — the classic bearing material
High strength, excellent machinability
Marine grade, corrosion resistant
Excellent embeddability, high loads
Pure Copper Properties
| Symbol | Cu |
| Atomic Number | 29 |
| Density | 8.96 g/cm³ |
| Melting Point | 1085°C (1984°F) |
| Thermal Conductivity | 401 W/m·K |
| Electrical Conductivity | 100% IACS |
| Tensile Strength | 210 MPa (annealed) |
| Hardness | HB 35-45 |
| Color | Reddish-orange |
Why Not Pure Copper?
Pure copper is too soft for most bearing applications and tends to gall (cold weld) against steel shafts. Alloying with tin, zinc, or lead dramatically improves bearing properties while retaining copper's thermal and corrosion benefits.
Why Copper is Essential for Bearing Alloys
Copper provides unique properties that make it the ideal base for bearing materials. Here's what copper contributes to bearing alloy performance.
Thermal Conductivity
401 W/m·K
Second only to silver. Copper rapidly dissipates friction heat from the bearing surface, preventing hot spots and lubricant breakdown.
Corrosion Resistance
Excellent
Copper forms a protective patina that resists further corrosion. Copper alloys excel in marine, chemical, and wet environments.
Conformability
High
Copper's ductility allows bearings to conform to shaft imperfections and misalignment, distributing load evenly across the surface.
Embeddability
Good
Soft copper matrix can embed dirt particles and debris, preventing shaft damage. Critical for contaminated environments.
Machinability
Excellent
Copper alloys machine easily with good surface finish. Reduces manufacturing costs and allows precision tolerances.
Antimicrobial
Natural
Copper naturally kills bacteria and viruses. Important for food processing, medical, and sanitary applications.
Common Copper Alloys for Bearings
Different alloying elements give copper-based bearings specific properties. Here's how the major copper alloy families compare for bearing applications.
| Alloy Type | Composition | Key Properties | Typical Applications | JBM Products |
|---|---|---|---|---|
| Tin Bronze | Cu + 10-12% Sn | Excellent wear resistance, high load capacity | Heavy machinery, gears, worm wheels | Cast Bronze |
| Phosphor Bronze | Cu + 5-10% Sn + P | High fatigue strength, spring properties | Wrapped bearings, springs, electrical | Wrapped Bronze |
| Lead Bronze | Cu + 10% Sn + 10% Pb | Excellent embeddability, anti-seizure | Engine bearings, high-load bushings | Bimetal |
| Aluminum Bronze | Cu + 9-14% Al | High strength, seawater resistant | Marine, heavy duty, corrosive environments | JBM-820 |
| High-Tensile Brass | Cu + 25% Zn + Al | Very high strength, impact resistant | Heavy load, slow speed, graphite plugged | Graphite Plugged |
| Gunmetal | Cu + 10% Sn + 2% Zn | Good all-round properties, castable | Valves, pumps, general engineering | Cast Bronze |
Lead-Free Copper Alloy Bearings
Traditional lead bronze bearings offer excellent performance but face increasing environmental restrictions. JBM offers RoHS-compliant lead-free alternatives.
Why Lead in Bearings?
Lead has traditionally been added to bronze bearing alloys because it:
- Improves machinability — lead acts as a chip breaker
- Provides lubricity — lead smears to form a lubricating film
- Enhances embeddability — soft lead absorbs contaminants
- Prevents seizure — lead layer protects during oil film breakdown
Lead-Free Alternatives
JBM offers lead-free copper alloys that meet RoHS and environmental regulations:
- CuSn8Ni — Nickel replaces lead for improved wear
- CuSn8Bi — Bismuth provides similar machinability
- CuAl10Ni — Aluminum bronze, naturally lead-free
- PTFE-lined — Polymer surface eliminates need for lead
Copper Alloys vs. Other Bearing Materials
| Property | Copper Alloys (Bronze) | Steel | Aluminum | Polymers (PTFE) |
|---|---|---|---|---|
| Load Capacity | Very High | Very High | Low-Medium | Medium |
| Thermal Conductivity | Excellent | Good | Excellent | Poor |
| Corrosion Resistance | Good-Excellent | Poor | Good | Excellent |
| Self-Lubricating | With graphite plugs | No | No | Yes |
| Machinability | Excellent | Good | Excellent | Good |
| Impact Resistance | Excellent | Good | Fair | Fair |
| Temperature Range | -40°C to +300°C | -40°C to +400°C | -40°C to +150°C | -200°C to +280°C |
| Cost | Medium-High | Low | Medium | Medium |
| Best For | Heavy loads, high temps | Ball/roller bearings | Lightweight apps | Maintenance-free |
Where Copper-Based Bearings Excel
Copper alloy bearings are the workhorses of heavy industry — handling high loads, shock, and demanding conditions where other materials fail.
Heavy Machinery
- Excavator bushings
- Crane pivot bearings
- Press slide guides
- Rolling mill chocks
- Crusher bearings
Marine & Offshore
- Rudder bearings
- Propeller shaft bushings
- Winch bearings
- Deck crane pivots
- Offshore equipment
Automotive
- Engine main bearings
- Connecting rod bearings
- Camshaft bushings
- Transmission bearings
- Suspension bushings
Power Generation
- Turbine bearings
- Generator bushings
- Hydropower equipment
- Wind turbine yaw bearings
- Steam valve guides
Steel & Metallurgy
- Furnace car bearings
- Ladle bearings
- Caster roll bushings
- Coiler mandrels
- Hot strip mill guides
Food & Beverage
- Mixer bearings
- Conveyor bushings
- Packaging equipment
- Bottling line bearings
- Bakery equipment
Copper-Based Bearing Solutions
Cast Bronze Bushings
Machined from solid bronze bar stock. Multiple alloy grades for various load and speed requirements.
Learn More →Wrapped Bronze Bushings
CuSn8 phosphor bronze strip wrapped into thin-wall bushings. Diamond oil pockets for lubrication.
Learn More →Bimetal Bushings
Steel backing with sintered bronze lining. High load capacity with lead-free options available.
Learn More →Graphite Plugged Bronze
Cast bronze with embedded graphite plugs for self-lubricating, maintenance-free operation.
Learn More →Oil-Impregnated Bronze
Sintered bronze bushings vacuum-impregnated with oil. Self-lubricating for motors and appliances.
Learn More →Steel Backed Bronze
Steel shell with bronze lining for automotive and construction equipment applications.
Learn More →Need help selecting the right copper alloy for your application? Our engineers can recommend the optimal material.
Contact EngineeringNeed Copper Alloy Bearings?
JBM manufactures a complete range of copper-based bearings — from cast bronze to wrapped phosphor bronze to bimetal bushings. Get the right alloy for your specific load, speed, and environmental requirements.
Request a Quote