Bearings + Bushings
Bearings and bushings support shafts, guide motion, reduce friction, and help control the relationship between moving machine elements. Selecting the correct component requires consideration of load direction, speed, motion type, lubrication, material, fit, alignment, and operating environment.
Common Bearing + Bushing Types
Motion-support components are available in many forms. The correct configuration depends on how a shaft or moving member travels, how loads are applied, and the performance required from the assembly.
Ball Bearings
Ball bearings use rolling elements between inner and outer races to reduce friction during rotary motion. Different designs accommodate varying radial, axial, speed, and alignment requirements.
Roller Bearings
Roller bearings use cylindrical, tapered, spherical, or needle-shaped rolling elements and are often selected where greater load capacity or specific load directions must be supported.
Linear Bearings
Linear bearings support movement along shafts, rails, or guides. They are commonly used in positioning systems, automation equipment, machine tools, and motion-control assemblies.
Sleeve Bushings
Sleeve bushings provide a sliding bearing surface between moving components. Their simple construction can offer compact packaging, low cost, and reliable operation in suitable speed and load ranges.
Flanged Bushings
Flanged bushings combine a cylindrical bearing surface with an integral flange that can provide axial location, support, spacing, or thrust control.
Thrust Bearings
Thrust bearings are designed primarily for axial loads acting along the shaft axis. Different rolling-element and sliding designs are used depending on speed and load.
Bearings vs. Bushings
Both component types reduce friction and support motion, but they accomplish that task differently. Neither is universally better; application requirements determine which approach is appropriate.
Rolling contact
Bearings typically use balls or rollers to separate moving surfaces. Rolling contact can support high rotational speeds and provide low friction when the bearing is properly selected and installed.
- Low rolling friction
- Suitable for many higher-speed applications
- Defined radial and axial load capacities
- Often requires precise shaft and housing fits
- May use grease or oil lubrication
Sliding contact
Bushings create a sliding interface between moving surfaces. Depending on material and design, they may operate with external lubrication, embedded lubricants, or self-lubricating bearing materials.
- Simple and compact construction
- Useful in oscillating or lower-speed movement
- Can tolerate contamination in suitable designs
- Available in many metallic and polymer materials
- Can provide economical motion support
Load direction changes the selection.
Bearings must support forces generated by the machine while allowing the required movement. The direction and magnitude of those forces affect bearing geometry, capacity, life, and installation.
Combined loading, shock, vibration, and misalignment can make selection more complex than a simple shaft diameter match.
Materials + Bearing Surfaces
Material choice affects load capacity, friction, corrosion resistance, wear, lubrication requirements, temperature capability, electrical properties, and suitability for contaminated environments.
Bearing Steel
Hardened bearing steels are widely used for rolling elements and races because they combine hardness, fatigue resistance, and dimensional stability.
Stainless Steel
Stainless bearing components can provide improved corrosion resistance for moisture, washdown, or certain process environments.
Bronze
Bronze is commonly used for bushings because of its wear characteristics, machinability, load capability, and compatibility with lubricated sliding interfaces.
Engineered Polymers
Polymer bushings may provide low friction, corrosion resistance, reduced weight, and operation without conventional external lubrication.
Ceramics
Ceramic rolling elements and bearing components may be selected for electrical isolation, high-speed operation, corrosion resistance, or specialized environments.
Composite Materials
Layered and composite bushing materials can combine structural support with low-friction bearing surfaces and embedded lubrication characteristics.
Bearing + Bushing Selection Factors
A replacement bearing should not be selected from outside diameter alone. Internal geometry, width, shaft fit, housing fit, load capability, speed, lubrication, and operating conditions must also be evaluated.
Compare load, fit, speed, and lubrication.
The Bearing & Bushing Selection Guide expands on bearing life, load direction, fit, clearances, lubrication, materials, shaft requirements, and replacement compatibility.
Related Motion Resources
These references provide additional information on linear movement, guided motion, bearing materials, and mechanical systems that commonly use bearings and bushings.
Supporting resources for guided linear movement and positioning assemblies.
Related resources involving specialty materials used in motion-support components.
Components and systems frequently operating alongside bearings, shafts, and guided motion hardware.