Types of Bearings: A Complete Guide

Any moveable mechanical system you see out there uses some kind of bearing in it. The use of bearings not only makes it easy to move around the system but adds a whole lot of benefit and functionality to it. 

In this guide, we will discover the various types of bearings that are used and available out there. And it’s not just the types, we talk about materials, manufacturing techniques, and so on. In short, it’s a complete guide to bearings. Let’s get started. 

What is Bearing?

A bearing is a mechanical component that reduces friction between moving parts, supporting rotational or linear movement. 

The primary functions of bearings include:

• Friction Reduction: By minimizing friction between moving parts, bearings help conserve energy and reduce wear and tear on components.
• Load Support: Bearings are designed to support both radial loads (perpendicular to the shaft) and thrust loads (parallel to the shaft).
• Precision: In many applications, bearings ensure precise movement and positioning of components.
• Speed Enhancement: By reducing friction, bearings allow for higher rotational or linear speeds in machinery.
• Noise and Vibration Reduction: Well-designed bearings can significantly decrease noise and vibration in mechanical systems.

Types of Bearings

The world of bearings is diverse, with each type designed to meet specific requirements in various applications. Here’s an overview of each type –

1. Ball Bearings

Ball bearings are perhaps the most common type of bearing you’ll come across. They use spherical balls as rolling elements between the two races.

Characteristics:

• Suitable for both radial and thrust loads
• High-speed capability
• Low friction
• Require minimal maintenance

Applications:

• Automotive wheel bearings
• Electric motors
• Hard disk drives
• Inline skates

Subtypes:

• Deep groove ball bearings
• Angular contact ball bearings
• Self-aligning ball bearings

2. Roller Bearings

Roller bearings use cylinders instead of balls as rolling elements. This design allows them to support heavier loads than ball bearings of similar size.

Characteristics:

• Higher load capacity than ball bearings
• Suitable for applications with shock or impact loading
• Lower maximum speed compared to ball bearings

Applications:

• Heavy machinery
• Conveyor systems
• Automotive transmissions
• Railroad car wheels

Subtypes:

• Cylindrical roller bearings
• Tapered roller bearings
• Needle roller bearings
• Spherical roller bearings

3. Plain Bearings (Bushings)

Plain bearings, also known as bushings, are the simplest type of bearing. They don’t have rolling elements; instead, they rely on a smooth surface for the shaft to rotate within.

Characteristics:

• Simple design
• Cost-effective
• Compact
• Can operate in dirty environments

Applications:

• Door hinges
• Pedal bushings on bicycles
• Small electric motors
• Automotive suspension systems

Subtypes:

• Journal bearings
• Linear bushings
• Thrust washers

4. Jewel Bearings

Jewel bearings use hard gemstones (usually synthetic sapphire) as a bearing surface. They’re typically used in precision instruments where low friction is crucial.

Characteristics:

• Extremely low friction
• High precision
• Long-lasting

Applications:

• Analog watches
• Sensitive measuring instruments
• Gyroscopes

5. Fluid Bearings

Fluid bearings use a thin film of gas or liquid to provide low friction support between surfaces.

Characteristics:

• Near-zero friction
• Can operate at very high speeds
• Quiet operation
• Require a constant supply of pressurized fluid

Applications:

• Hard disk drives
• Precision machine tools
• Large telescopes
• Some hydroelectric generators

Subtypes:

• Hydrostatic bearings
• Hydrodynamic bearings
• Aerostatic bearings
• Aerodynamic bearings

6. Magnetic Bearings

Magnetic bearings use magnetic fields to support a rotating shaft without physical contact.

Characteristics:

• No physical contact, therefore no friction
• Can operate at extremely high speeds
• Require complex control systems
• High initial cost

Applications:

• Flywheel energy storage systems
• Turbo-molecular pumps
• Some types of compressors
• Advanced machine tools

7. Thrust Bearings

Thrust bearings are specifically designed to support axial loads (forces parallel to the shaft).

Characteristics:

• Specifically designed for axial loads
• Can support heavy loads in one direction

Applications:

• Helicopter rotors
• Vertical pumps
• Propeller shafts in ships

Subtypes:

• Ball thrust bearings
• Roller thrust bearings
• Tapered roller thrust bearings

How to Choose Bearings in Manufacturing?

Selecting the right bearing for your application is crucial for ensuring optimal performance, longevity, and cost-effectiveness of your mechanical system. Here are the key factors you need to consider when choosing bearings for manufacturing:

Load Type and Magnitude

The first thing you need to consider is the type and magnitude of the load your bearing will need to support:

• Radial Load: Forces perpendicular to the shaft
• Axial (Thrust) Load: Forces parallel to the shaft
• Combined Load: A combination of radial and axial loads

You must calculate the maximum load the bearing will experience during operation. This includes not just the steady-state load, but also any shock loads or temporary overloads.

Speed Requirements

Different bearings have different speed capabilities. You need to consider:

• The maximum speed at which the bearing will operate
• Whether the speed will be constant or variable
• If there are frequent start-stop cycles

Ball bearings generally offer the highest speed capabilities, while roller bearings are better suited for lower speeds but higher loads.

Operating Environment

The environment in which the bearing will operate significantly impacts your choice:

• Temperature: Extreme heat or cold can affect bearing performance and lifespan
• Moisture: High humidity or exposure to liquids may require sealed or shielded bearings
• Contamination: The presence of dust, dirt, or other particles may necessitate special sealing arrangements
• Vibration: High-vibration environments may require bearings with higher durability

Precision Requirements

Some applications require extremely precise positioning or movement:

• Runout: The amount of deviation from the true rotational center
• Torque Variation: Consistency of rotational resistance
• Noise Level: Some applications require ultra-quiet operation

For high-precision applications, you might need to consider ABEC (Annular Bearing Engineering Committee) ratings, which indicate the manufacturing tolerances of the bearing.

Space Constraints

The available space in your design can limit your bearing options:

• Shaft Diameter: This often determines the inner diameter of the bearing
• Housing Size: This limits the outer diameter and width of the bearing
• Weight Limitations: In some applications, the weight of the bearing itself might be a critical factor

Lubrication

Consider how the bearing will be lubricated:

• Grease: Suitable for many applications, requires less frequent maintenance
• Oil: Better for high-speed or high-temperature applications
• Solid Lubricants: Used in extreme environments where conventional lubricants would fail
• Self-Lubricating Materials: Used in plain bearings for low-load, low-speed applications

Life Expectancy and Reliability

You need to determine how long the bearing needs to last and how critical its function is:

• Calculate the L10 life (the number of revolutions 90% of a group of identical bearings will complete before showing signs of fatigue)
• Consider the consequences of bearing failure and whether redundancy is necessary

Cost Considerations

While it’s tempting to always go for the highest quality bearing, you need to balance performance with cost:

• Initial purchase cost
• Installation cost
• Maintenance cost
• Replacement cost and frequency

What Materials Are Used for Bearings?

The materials used in bearing construction play a crucial role in determining their performance, durability, and suitability for different applications. Here’s an overview of the most common materials used in bearing manufacturing:

Steel

Steel is by far the most common material used in bearing production due to its excellent combination of strength, hardness, and affordability.

Types of Steel Used:

• Chrome Steel
• Stainless Steel
• Tool Steel
• Case-Hardened Steel

Advantages of Steel:

• High strength and hardness
• Good wear resistance
• Relatively low cost
• A wide range of grades available for different applications

Disadvantages:

• Can be heavy
• Susceptible to corrosion (except stainless steel)
• Can be brittle, especially at low temperatures

Ceramics

Ceramic materials, particularly silicon nitride (Si3N4), are increasingly used in high-performance bearings.

Advantages of Ceramics:

• Extremely hard and wear-resistant
• Low density (lighter than steel)
• Can operate at higher temperatures than steel
• Electrically insulating
• Corrosion-resistant

Disadvantages:

• More expensive than steel
• Can be brittle and sensitive to shock loads
• More difficult to manufacture to precise tolerances

Applications: Ceramic bearings are often used in high-speed machine tool spindles, racing bicycles, and some aerospace applications.

Plastics

Various plastics are used for bearings, especially in low-load, low-speed applications or corrosive environments.

Common Plastics Used:

• PTFE (Teflon)
• Nylon
• Acetal (POM)
• PEEK (Polyether ether ketone)

Advantages of Plastics:

• Low friction
• Lightweight
• Corrosion-resistant
• Can operate without lubrication in some cases
• Low noise operation

Disadvantages:

• Lower load capacity than metal bearings
• Limited temperature range
• Lower precision than metal bearings

Applications: Plastic bearings are often used in food processing equipment, chemical pumps, and other applications where corrosion resistance is crucial.

Babbitt Metal

Babbitt metal is a soft alloy traditionally used in plain bearings. It’s typically made of tin or lead alloyed with copper, antimony, and other metals.

Advantages of Babbitt Metal:

• Excellent conformability
• Good embeddability (can embed dirt particles)
• Low friction

Disadvantages:

• Low load capacity
• Limited to low-speed applications
• Can creep under heavy loads

Applications: Babbitt metal is still used in some large industrial machinery, particularly in older equipment.

Bronze

Bronze alloys are commonly used in plain bearings and bushings.

Advantages of Bronze:

• Good strength
• Excellent corrosion resistance
• Can be used with steel shafts without galling
• Self-lubricating properties when manufactured with graphite inserts

Disadvantages:

• More expensive than steel
• Lower hardness than steel

Applications: Bronze bearings are often used in marine environments, food processing equipment, and other applications where corrosion resistance is important.

Composite Materials

Various composite materials are used in modern bearing design, often combining the properties of different materials.

Examples:

• Fiber-reinforced polymers
• Metal-polymer composites
• Ceramic-coated metals

Advantages of Composites:

• Can be tailored to specific application requirements
• Often combine high strength with low weight
• Can offer unique combinations of properties (e.g., high strength and corrosion resistance)

Disadvantages:

• Can be expensive
• May have complex manufacturing processes

Applications: Composite bearings are used in a wide range of specialized applications, from aerospace to chemical processing.

How to Manufacture Bearings?

You can try out various techniques to create different kinds of various. Here’s a quick overview of some modern techniques that can be used for manufacturing bearings. 

CNC Machining

Computer Numerical Control (CNC) machining is at the heart of modern bearing manufacturing:

• Multi-Axis CNC Machines: These allow for complex geometries to be machined in a single setup, improving accuracy and reducing production time.
• High-Speed Machining: Enables faster material removal rates while maintaining high precision.
• Adaptive Machining: Uses real-time feedback to adjust cutting parameters, ensuring consistency across parts.

Precision Grinding

Grinding is a critical process in bearing manufacturing, used to achieve precise dimensions and smooth surfaces:

• Centerless Grinding: Often used for rollers and needles, this technique can achieve roundness tolerances as tight as 0.5 micrometers.
• Superfinishing: A specialized abrasive process that can produce surface roughness as low as 0.05 micrometers Ra (arithmetic average roughness).
• Honing: Used to improve the geometry and surface finish of bearing bores and outer diameters.

Electrical Discharge Machining (EDM)

EDM is used for creating complex shapes in hardened materials:

• Wire EDM: Can cut intricate profiles in bearing components, particularly useful for cages and special bearings.
• Sinker EDM: Used for creating precise cavities or features in bearing components.

Laser Machining

Laser technology is increasingly used in bearing manufacturing:

• Laser Cutting: For precise cutting of thin materials, often used in cage manufacturing.
• Laser Marking: For adding identification marks or scales to bearing components.
• Laser Heat Treatment: This can be used for localized hardening of bearing surfaces.

Precision Measurement and Inspection

While not a machining technique per se, precision measurement is integral to the machining process:

• Coordinate Measuring Machines (CMM): Used for highly accurate 3D measurements of bearing components.
• Optical Measurement Systems: Non-contact measurement for rapid inspection of surface quality and dimensions.
• Roundness Testers: Specialized equipment for measuring the roundness of balls, rollers, and raceways.

Microfinishing

Also known as tape finishing or stone finishing, this technique is used to achieve extremely smooth surfaces:

• Can produce surface finishes as fine as 0.025 micrometers Ra.
• Particularly important for high-speed bearings where even tiny surface imperfections can cause noise and vibration.

Precision Lapping

Lapping is used to produce extremely flat or smooth surfaces:

• Often used for thrust-bearing races and some roller ends.
• Can achieve flatness tolerances of less than 1 micrometer.

Precision Boring

For bearings with bores, precision boring is crucial:

• CNC boring bars with active vibration damping can achieve very tight tolerances.
• Important for ensuring proper fit between the bearing and the shaft.

Conclusion

To conclude, now you know about the different types of bearings and even know how they are made. If you are looking to start manufacturing some with the help of a service, then Zintilon can be a perfect partner for your bearing manufacturing project. Whether it be with CNC machining or EDM, they have everything to offer.