How to Choose the Right Bearings: Key Factors for Engineers

When it comes to ensuring the reliability and efficiency of machine operation, selecting the right bearing is important. It’s not just about finding a part that fits—it’s about understanding how key factors like speed, fit, mounting, and maintenance directly impact your system’s overall performance. At PIB Sales, we specialize in providing high-quality RBC bearings engineered to meet the most demanding requirements.

Types of Bearings and Their Applications

RBC Bearings, a leading provider of high-quality bearings, designs a comprehensive range of bearing solutions for various industrial applications. RBC Bearings are engineered to meet the most demanding performance, durability, and reliability requirements from aerospace to automotive and industrial machinery. Each bearing type in RBC’s portfolio is crafted to handle specific operational conditions such as high loads, speeds, and specific motion characteristics. Below, we will explore the technical details of each bearing type offered by RBC Bearings and their optimal use cases.

Roller Bearings are designed to carry heavy radial loads using cylindrical, spherical, or tapered rollers. Compared to ball bearings, roller bearings have a larger surface area contact, allowing them to handle higher radial forces and operate at lower friction levels. The roller design ensures better load distribution, which enhances the bearing’s overall capacity and operational life. Roller bearings are often chosen for applications where significant radial loads or higher operational reliability are required.

Applications:

• Industrial machinery: common in conveyors, crushers, and presses, where heavy radial loads are frequent.
• Automotive: used in wheel hubs, transmissions, and gearbox applications that experience substantial radial forces.
• Aerospace: employed in landing gear systems and other aircraft components where high-load capacity is essential.

Tapered Roller Bearings bearings are designed to accommodate both radial and axial loads simultaneously. The rollers are conically shaped, which allows them to handle combined loading forces effectively. These bearings are often used in high-load applications and where axial loads are present in addition to radial loads. Tapered roller bearings are available in various designs, including single-row, double-row, and four-row configurations, allowing them to support different load capacities and operational conditions.

Applications:

• Automotive: commonly used in wheel hubs, transmissions, and differential gears, where both radial and axial loads are present.
• Industrial equipment: ideal for gearboxes, rotary systems, and gear drives that require both types of load handling.
• Aerospace: used in aircraft systems where both axial and radial forces are encountered, such as in the main gear and engine assemblies.
• Airframe control bearings are specialized bearings designed to support the control surfaces and mechanisms in an aircraft. These bearings are optimized for precision, high load capacity, and reliability under extreme conditions, such as temperature variations, shock loads, and high-speed rotations. Airframe control bearings are typically made from high-strength materials like stainless steel or other corrosion-resistant alloys to withstand the harsh environment in which they operate.

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Thin-section ball bearings are designed with a thin outer ring and reduced width compared to standard bearings, allowing them to perform in confined spaces without sacrificing load capacity. These bearings offer low radial and axial clearance, which makes them ideal for applications requiring high precision in rotation, especially where space is limited. They are highly resistant to vibration and provide long-lasting, smooth performance under moderate to high-speed conditions.

Applications:

• Robotics: used in robotic arms, actuators, and precision rotary stages where compact design and high precision are necessary.
• Medical equipment: found in MRI machines, dental tools, and other medical instruments where space constraints and precision are crucial.
• Aerospace: used in satellite systems, actuators, and other aerospace applications that require compact, reliable bearings.

Rod end bearings are used to connect a rod or shaft to a machine or structure. These bearings typically feature a spherical bearing inside a housing, allowing them to accommodate angular misalignments. Rod end bearings are designed for use in applications that involve oscillating motion and are frequently used in linkages, steering systems, and suspension systems. They offer high strength and durability while allowing for movement in multiple directions.

Applications:

• Automotive: rod end bearings are widely used in steering and suspension systems where precise motion is required.
• Aerospace: these bearings are used in flight control systems, actuators, and landing gear mechanisms, where high strength and smooth operation are essential.
• Industrial machinery: found in conveyors, cranes, and other equipment where motion is needed between rods and shafts.

Thrust bearings are specifically designed to handle axial loads, where forces are applied parallel to the axis of rotation. These bearings consist of two thrust plates, between which are ball or roller elements that support the axial load. Thrust bearings are often used when high axial load capacities are required without significant radial load involvement. There are multiple types of thrust bearings, including thrust ball bearings, roller thrust bearings, and tapered thrust bearings.

Applications:

• Automotive: used in transmissions, clutches, and other components where axial loads need to be managed.
• Industrial: common in gearboxes, pumps, and turbines where axial forces are predominant.
• Aerospace: used in aircraft engine components and landing gear systems where axial loads are experienced.

Cam followers and yoke rollers are specially designed for applications where rotary motion and axial load handling are required simultaneously. These bearings are equipped with a cylindrical roller or needle design that allows them to handle high axial and radial loads. Cam followers are often used in systems that require rolling motion, while yoke rollers are designed for linear motion and offer precise control and smooth operation.

Applications:

• Industrial equipment: used in automated machinery, conveyor systems, and cam-driven mechanisms where smooth rolling motion is necessary.
• Automotive: found in valve actuators, camshaft systems, and other automotive mechanisms requiring reliable rolling motion.
• Robotics: employed in robotic arms and linear actuators where smooth movement is essential.

RBC Heim Bearings specializes in rod ends and spherical bearings that are designed for high-stress, precision applications. These bearings are often used in systems that require motion flexibility, where angular misalignments or complex loads are present. RBC Heim bearings are widely known for their durability and performance in demanding environments.

Applications:

• Aerospace: critical in high-load, high-precision applications, such as flight control systems and landing gear.
• Industrial machinery: used in linkages, steering systems, and robotics.
• Defense and military: applied in advanced weaponry systems and military vehicles requiring high-strength, precise movement.

Needle roller cam follower bearings are a compact design that uses needle rollers to handle both radial and axial loads. These bearings are ideal for applications requiring high load capacity in a compact footprint. They are commonly used in camshaft systems and other mechanisms requiring precise rotational movement.

Applications:

• Industrial machinery: used in cam-driven machinery, such as presses and automated equipment.
• Automotive: found in camshafts and valve systems where compact bearing solutions are required.
• Robotics: employed in actuators and robotic joints where precision and load capacity are critical.

Track rollers are designed to support linear motion in rail or track systems. These bearings typically feature a large outer diameter and a thick, robust design, allowing them to handle substantial radial loads. Track rollers are commonly used in applications where machinery moves along a fixed track or rail.

Applications:

• Industrial equipment: used in conveyor systems, rolling stock, and other machinery that requires stable motion along a track or rail.
• Construction equipment: found in earth-moving machinery such as bulldozers, excavators, and cranes, where heavy loads are transferred along tracks.
• Aerospace and defense: used in specialized applications like military vehicles and launch systems where linear motion is essential.

RBC bearings part numbers and technical specifications

The following table provides each bearing type’s part numbers and essential technical specifications. This information can help make an informed choice based on the specific needs:

Considering Speed in Bearing Selection

The speed at which a bearing operates directly impacts the type of bearing needed, its material composition, lubrication requirements, and design. Bearings designed for high-speed applications must be capable of withstanding the increased heat and centrifugal forces generated at higher velocities. On the other hand, bearings used in low-speed applications might prioritize load capacity and durability over speed tolerance.

Below are key considerations and tips for selecting the right bearing based on the operating speed of your application:

Choose bearings with appropriate speed ratings
Every bearing type has a specified maximum operating speed, which is typically defined by its limiting speed or the “maximum permissible speed.” It’s essential to choose a bearing that meets or exceeds the required speed for your application. Exceeding the rated speed can lead to overheating and premature failure. Always check the manufacturer’s speed ratings, and consult technical data for specific models.
Tip: look for bearings that are specifically designed for high-speed applications, such as special material high-speed ball bearings or ceramic ball bearings that can handle higher rotational velocities without compromising performance.

Consider lubrication requirements
At high speeds, friction, and heat generation become more significant, making proper lubrication critical. Insufficient lubrication can cause metal-to-metal contact, leading to rapid wear and bearing failure. For high-speed applications, grease or oil lubrication must be able to dissipate heat and maintain a stable viscosity.
Tip: for high-speed applications, select bearings with high-performance lubrication options (such as synthetic oils or greases), which are specially formulated to withstand the higher temperatures generated by faster rotations.

Bearings with special materials for high speeds
Bearings made from high-performance materials are better suited for handling the stresses generated by high-speed rotations. Materials such as ceramics or hybrid bearings (combining steel and ceramic balls) can withstand higher speeds and temperatures due to their lower friction coefficients and greater thermal resistance.
Tip: when operating at speeds exceeding 20,000 RPM, consider ceramic hybrid bearings (e.g., Si3N4 balls) or full ceramic bearings, as these materials significantly reduce friction and minimize heat generation.

Understand the importance of internal clearances
Bearings with larger internal clearances (or radial play) are more appropriate for low-speed applications where the bearing will not experience significant expansion due to heat. However, in high-speed applications, it’s important to select bearings with smaller internal clearances to reduce vibration and prevent excessive movement within the bearing, which could lead to wear.
Tip: for high-speed systems, select bearings with C2 or C3 clearance ratings (depending on the application), which ensure a tighter fit to reduce heat and vibration issues.

Account for thermal expansion
In high-speed applications, the bearing components may expand due to the heat generated by friction. Bearings designed for high-speed applications should have the ability to tolerate thermal expansion without losing their integrity. Materials like ceramic or specialized high-speed steels are capable of maintaining their dimensional stability even under elevated temperatures.
Tip: ensure that the bearing material has a low coefficient of thermal expansion (CTE), especially if the bearing will be exposed to significant heat. Ceramic bearings are often used in high-speed, high-temperature applications because they have extremely low CTE, minimizing thermal growth.

Monitor the effect of centrifugal forces
As the speed increases, the centrifugal forces acting on the bearing’s rolling elements also increase. These forces can lead to deformation of the rolling elements, reduced precision, and higher wear rates. In high-speed bearings, the internal design and materials must be capable of handling these forces without compromising performance.
Tip: bearings with low-friction coatings or hybrid designs (combining steel and ceramic) help mitigate the effects of centrifugal forces and reduce overall wear rates in high-speed applications.

Choosing Bearings Based on Fits

The fit between a bearing and its shaft or housing directly influences the bearing’s ability to withstand operational stresses, distribute loads effectively, and maintain alignment throughout its lifespan. A poorly chosen fit can lead to misalignment, excessive wear, or failure. Therefore, choosing the correct fit requires a clear understanding of the operating conditions and the technical implications of each fit type.

Understanding bearing fits

The term “fit” refers to the relationship between the bearing’s inner and outer rings and the mating surfaces of the shaft and housing. The fit can significantly affect the performance of the bearing under various operational conditions, such as load, speed, and temperature. There are three primary types of fits used in bearing applications: interference fit, transition fit, and clearance fit. Each type serves a specific purpose, and the choice depends on factors like load distribution, rotational speed, and the potential for thermal expansion or movement.

Interference fit, often referred to as a press fit, is where the bearing’s inner or outer ring has a slightly larger diameter than the mating shaft or housing. This type of fit ensures a secure, tight connection that prevents any axial or radial movement of the bearing. Interference fits are commonly used in high-load and high-speed applications where stability and precision are paramount.

In applications such as automotive wheel hubs or machine tool spindles, where bearing movement could lead to misalignment and premature failure, an interference fit is ideal. However, the amount of interference must be carefully calculated to avoid overstressing the bearing or causing deformation. Too tight a fit can lead to excessive friction or damage, while too loose a fit may result in slippage under load.

A transition fit is a middle ground between an interference fit and a clearance fit. With a transition fit, the bearing may have slight interference or a very tight clearance, ensuring it stays in place under moderate load but can be disassembled with some effort. This fit is often used in applications where ease of assembly and disassembly are important, but some bearing stability is still required.

In scenarios where bearings need to be periodically replaced or adjusted, such as in industrial machinery, a transition fit can strike the right balance between secure positioning and maintenance flexibility. While it provides more flexibility than an interference fit, it still offers a relatively tight connection that helps prevent bearing slippage during operation.

Clearance fit allows the bearing to slide or rotate freely within the housing, creating a gap between the bearing and its mating components. This type of fit is used when slight axial or radial movement is acceptable or when thermal expansion could affect the fit. Clearance fits are often chosen for low-load, low-speed applications, or when ease of assembly is a key consideration.

In applications such as simple support systems or parts requiring frequent disassembly, a clearance fit ensures that bearings can be easily installed or replaced. However, this fit is less suited for high-speed or heavy-load applications, as it can result in misalignment and increased friction over time if not managed properly.

Step-by-Step Process for Choosing the Right Fit

To summarize the process, here’s a simplified guide for selecting the right bearing fit based on application requirements:

1. High-speed, high-load applications typically require a more secure interference fit, while low-load, low-speed systems may be suitable for clearance fits.
2. In environments where thermal expansion is a factor, such as motors or turbines, a clearance fit or transition fit is often preferred to accommodate temperature-induced changes.
3. If the bearing needs to be replaced or adjusted periodically, a transition or clearance fit may offer greater flexibility in terms of assembly and disassembly.
4. Carefully calculate the tolerances for the bearing and mating parts to avoid excessive stress on the bearing material, ensuring it performs optimally over its lifespan.

Mounting and Installation Considerations

Even the highest-quality bearing can fail prematurely if not installed correctly. Below are expert recommendations for ensuring optimal bearing installation based on technical and engineering principles.

1. Ensure cleanliness before installation

Bearings are precision components, and contamination during installation can drastically reduce their lifespan. Always ensure that bearings are kept clean and free from dust, dirt, and oils. This includes the shaft, housing, and surrounding areas. Small particles can cause surface damage to raceways and rolling elements, leading to premature wear. Use clean tools and gloves, and store bearings in a clean, dry environment.

2. Check fit and tolerances

The fit between the bearing and the shaft or housing is crucial for proper functioning. Always check the manufacturer’s recommended tolerances for the specific bearing type and application. For interference fits, ensure that the shaft or housing is the correct size before applying force. For transition and clearance fits, confirm that there is minimal movement to avoid misalignment under load. If you’re working with tight fits, ensure the bearing is properly heated or the shaft is chilled, as this can simplify installation.

3. Use the correct mounting tools

Avoid using hammers or excessive force during installation, as these can damage both the bearing and surrounding components. Always use the appropriate mounting tools, such as bearing presses, induction heaters, or hydraulic presses, depending on the bearing type and fit. For larger bearings, especially those with interference fits, a press or hydraulic system should be used to apply even pressure. Never apply force directly to the rolling elements—only to the outer or inner ring, depending on the mounting configuration.

4. Control installation speed and force

Whether you are pressing, heating, or assembling bearings, always apply controlled, gradual force. Excessive force or sudden impacts can lead to bearing damage, such as brinelling (indentation of the raceways). Similarly, avoid rapid temperature changes during heating or cooling, as thermal shock can cause material stress or distortion. Apply the minimum necessary force to achieve secure mounting without compromising the bearing’s integrity.

5. Ensure proper lubrication

Before installation, ensure that the bearing is appropriately lubricated according to manufacturer guidelines. For high-speed applications, opt for low-viscosity oils or greases, while heavier greases may be better for load-bearing applications. Never install a bearing without the proper lubrication, as this can lead to excessive heat generation and failure.

For engineers, manufacturers, and OEMs looking to source high-quality RBC Bearings, all of these components and more are readily available through PIB Sales.
PIB Sales is a trusted distributor of RBC Bearings and other high-performance components, offering seamless ordering and fast delivery to meet your project requirements.
Explore the full range of RBC Bearings and place your order today at PIB Sales for your next project or system upgrade.