Sintered Bronze
Powder Metallurgy Bearing Material
A porous, self-lubricating bearing material created through powder metallurgy. Oil-impregnated sintered bronze bushings provide maintenance-free operation for millions of cycles.
What is Sintered Bronze?
Sintered bronze is a porous metallic material manufactured through powder metallurgy — a process where fine bronze powder is compacted under high pressure and then heated (sintered) below its melting point. The result is a solid metal structure with controlled porosity, typically 20-30% void volume.
This porous structure is the key to sintered bronze's self-lubricating capability. When vacuum-impregnated with oil, the interconnected pores act as tiny reservoirs. During operation, the oil is released to the bearing surface through capillary action, providing continuous lubrication without external maintenance.
JBM manufactures oil-impregnated bronze bushings using high-quality sintered bronze conforming to SAE 841 and other international standards. These bearings are ideal for small motors, appliances, power tools, and automotive applications where quiet, maintenance-free operation is essential.
Powder Metallurgy Process
Powder Mixing
Copper and tin powders blended to precise bronze composition (typically 90% Cu, 10% Sn)
Compacting
Powder pressed in dies at 200-400 MPa to form "green" compact with controlled density
Sintering
Heated to 750-850°C in reducing atmosphere. Particles bond without melting, preserving porosity
Sizing
Re-pressed to achieve final dimensions and surface finish tolerances
Oil Impregnation
Vacuum impregnated with lubricating oil (typically 18-25% oil content by volume)
Sintered Bronze Properties
| Composition | Cu 88-92%, Sn 8-12% |
| Density | 5.8 - 6.8 g/cm³ |
| Porosity | 20-30% (by volume) |
| Oil Content | 18-25% (by volume) |
| Hardness | HB 40-70 |
| Crush Strength | 200-350 N/mm² |
| Max Load | 15-20 N/mm² |
| Max Speed | 6 m/s (oil lubricated) |
| Temperature Range | -40°C to +120°C |
| Friction (Running) | 0.04 - 0.10 |
Industry Standards
- SAE 841 — Sintered Bronze (US)
- ASTM B438 — Grade 1, Type II
- MPIF CT-1000-K26
- ISO 5755 — CuSn10-C-20
- JIS Z 2550 — Type 1
How Oil-Impregnated Sintered Bronze Works
The porous structure of sintered bronze enables a continuous, self-sustaining lubrication cycle that provides maintenance-free operation throughout the bearing's service life.
Heat Generation
Shaft rotation creates friction at the bearing surface. This generates localized heat, causing the oil within the pores to expand.
Capillary Action
Thermal expansion and capillary forces draw oil from the porous matrix to the bearing surface, forming a lubricating film.
Hydrodynamic Film
Oil film separates the shaft from the bearing surface, reducing friction and wear. The shaft essentially "floats" on oil.
Oil Recirculation
When stationary, oil is reabsorbed into the pores by capillary action, ready for the next operating cycle. Self-sustaining system.
Why Porosity Matters
The porosity of sintered bronze is carefully controlled during manufacturing. Too little porosity means insufficient oil storage and early bearing failure. Too much porosity reduces strength and load capacity. The optimal 20-30% porosity balances oil capacity with mechanical properties.
Sintered Bearing Material Options
Different sintered materials are available for various load, speed, and environmental requirements. SAE 841 sintered bronze is the most common grade for general-purpose bearings.
| Property | SAE 841 Sintered Bronze | SAE 850 Bronze-Iron | SAE 863 Diluted Bronze | SAE 852 Sintered Iron |
|---|---|---|---|---|
| Composition | Cu 88%, Sn 10% | Cu 60%, Fe 35% | Cu 78%, Fe 10% | Fe 96%, Cu 2% |
| Density | 6.4-6.8 g/cm³ | 6.0-6.4 g/cm³ | 6.2-6.6 g/cm³ | 5.8-6.2 g/cm³ |
| Hardness | HB 45-65 | HB 50-75 | HB 40-60 | HB 55-85 |
| Max Load | 15 N/mm² | 20 N/mm² | 12 N/mm² | 25 N/mm² |
| Max Speed | 6 m/s | 4 m/s | 5 m/s | 3 m/s |
| PV Limit | 1.8 N/mm²·m/s | 1.4 N/mm²·m/s | 1.2 N/mm²·m/s | 1.0 N/mm²·m/s |
| Corrosion Resist. | Excellent | Good | Good | Poor |
| Cost | Medium-High | Medium | Medium | Low |
| Best For | General purpose, motors | Higher loads | Cost-sensitive | Heavy duty, low cost |
Why Choose Sintered Bronze Bearings
Maintenance-Free
Self-lubricating design eliminates the need for external lubrication. "Fit and forget" installation for sealed applications.
Quiet Operation
Oil film provides excellent damping. Ideal for noise-sensitive applications like appliances, office equipment, and medical devices.
Cost-Effective
Powder metallurgy enables high-volume production with minimal waste. Near-net-shape manufacturing reduces machining costs.
Tight Tolerances
Sizing operation achieves precise bore dimensions (±0.013mm typical). Consistent quality across high-volume production.
Corrosion Resistant
Bronze alloy provides natural resistance to corrosion. Oil impregnation adds additional protection against moisture.
High Speed Capable
Supports speeds up to 6 m/s with proper design. Hydrodynamic oil film ensures stable operation at high RPM.
Complex Shapes
Powder metallurgy allows economical production of flanged, spherical, and custom geometries without secondary machining.
Long Service Life
Millions of cycles without failure. Oil continuously recirculates, providing reliable lubrication throughout bearing life.
Need sintered bronze bearings for your application? We offer standard sizes and custom designs.
Get a QuoteSintered Bronze vs. Cast Bronze Bushings
Both are bronze materials, but they serve different applications. Understanding the differences helps you select the right bearing for your needs.
Sintered Bronze
- Self-lubricating (oil impregnated)
- Maintenance-free operation
- Cost-effective for high volumes
- Quiet operation
- Precise tolerances from mold
- Complex shapes economical
- Lower load capacity (15 N/mm²)
- Limited size range
- Cannot be machined easily
- Lower temperature limit
Best For: Small motors, appliances, power tools, automotive accessories, office equipment
Cast Bronze
- High load capacity (50+ N/mm²)
- Large sizes available
- Fully machinable
- Higher temperature capability
- Impact resistant
- Custom alloys available
- Requires external lubrication
- Higher cost for simple shapes
- More machining required
- Maintenance needed
Best For: Heavy equipment, construction, marine, industrial machinery, large shafts
Where Sintered Bronze Bearings Excel
Sintered bronze bushings are the preferred choice for light-to-medium duty, high-speed rotating applications where quiet, maintenance-free operation is essential.
Electric Motors
- Fractional HP motor bearings
- Fan motor bushings
- Pump motor bearings
- Servo motor supports
- Stepper motor bushings
Home Appliances
- Washing machine bearings
- Vacuum cleaner motors
- Kitchen appliances
- HVAC blower motors
- Refrigerator fans
Power Tools
- Drill motor bearings
- Saw blade supports
- Sander motor bushings
- Router bearings
- Grinder spindles
Automotive
- Starter motor bushings
- Wiper motor bearings
- Window regulator bushings
- Seat motor supports
- Mirror adjustment motors
Office Equipment
- Printer motor bearings
- Copier feed mechanisms
- Shredder motors
- Scanner drives
- Paper handling equipment
Industrial Equipment
- Conveyor idlers
- Small pumps
- Textile machinery
- Packaging equipment
- Food processing machines
Sintered Bronze Bushing Shapes
Cylindrical
Standard sleeve bushing. Press-fit into housing for radial load support.
ID: 2mm - 50mm
Flanged
Integral flange for axial location and thrust load support. Easy installation.
ID: 3mm - 40mm
Spherical
Self-aligning design compensates for shaft misalignment.
ID: 4mm - 25mm
Thrust Washer
Flat washer for axial thrust loads. Often used with cylindrical bushings.
OD: 8mm - 60mm
Need Sintered Bronze Bearings?
JBM supplies oil-impregnated sintered bronze bushings for motors, appliances, and industrial applications. Standard sizes ship quickly; custom designs available for OEM requirements.
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