Plain Bearings (Sliding Bearings) Overview and Applications

Plain bearings (also called sliding bearings) are a type of bearing without rolling elements. They operate through sliding friction to provide support and motion. Unlike rolling bearings, they are particularly well-suited for high load, low speed, or harsh environments (such as dust, humidity, and vibration).

Among the most widely used self-lubricating plain bearings are:

• Metal Graphite Bearings

• Bronze ASTM B271 C-86300 (SAE 430-B) Bearings with Self-Lubricating Inserts

These designs combine a metallic matrix with solid lubricants (such as graphite or polymer inserts), offering excellent wear resistance, corrosion resistance, and minimum maintenance requirements. Below, we discuss their typical applications, performance features, and recommended solutions.

1. Metal Graphite Bearings

Key Features:

• Structure: Copper or iron matrix with embedded graphite particles

• Self-lubrication: Continuous release of graphite during operation

• Heat resistance: Up to 300°C and beyond

• Friction coefficient: 0.1–0.2 under dry conditions

• Best suited for: Dry-running or intermittent lubrication environments

Typical Applications:

• Heavy machinery & construction equipment: Excavator swing joints, loader bucket linkages

• Agricultural & forestry equipment: Tractor guide rollers, harvester lifting arms

• Automotive & off-road vehicles: Suspension bushings, gearbox linkages (noise and vibration reduction)

• Industrial machinery: Machine tool spindles, conveyor rollers for continuous low-speed operation

Engineering Solutions:

• Graphite insert ratio: 20–30% for reliable initial lubrication

• Maintenance: No regular greasing required; wear check every 5,000–10,000 hours

• Cooling options: Integrate air or water cooling to extend service life

• Load capacity: 10–20 MPa

• Cost efficiency: About 30% lower than full ceramic bearings

2. Bronze ASTM B271 C-86300 (SAE 430-B) Self-Lubricating Bearings

Material Properties:

• Alloy composition: Cu 62–66%, Mn 2.5–5%, Fe 2–4%

• Hardness: HB 180–220

• Tensile strength: >650 MPa

• Temperature range: -40°C to +150°C

• High PV performance: Suitable for pressure × velocity >200 MPa·m/s

Typical Applications:

• Heavy-duty machinery: Hydraulic cylinder piston rods, wheel axle bearings

• Construction equipment: Excavator boom joints (corrosion and vibration resistance)

• Industrial presses: Stamping press guide columns, long-life with minimal lubrication

• Off-road vehicles: Brake calipers, drive shafts in dusty and wet conditions

Engineering Solutions:

• Insert coverage: 30–50% in high-friction zones

• Precision machining: CNC tolerance control ±0.01 mm

• Surface treatment: Phosphate coating increases fatigue resistance to 10⁶ cycles

• Durability: Up to 2× longer service life compared to standard bronze bearings

3. Application Types and Bearing Solutions

4. Bearing Selection and Industry Guidelines

• Selection principle:

  • Low PV applications → Metal Graphite Bearings

  • High PV applications → Bronze C86300 Bearings

• Installation & Testing:

  • Pre-press fit, clearance 0.05–0.1 mm

  • Run-in test for 100 hours to validate self-lubricating effect

• Industry recommendations:

  • Heavy-duty machinery: Prefer high-strength bronze bearings

  • Agricultural & automotive: Favor graphite-based designs for dust and dirt resistance