A self-aligning ball bearing is ideal for applications in which the shaft and housing are misaligned. Designed to accommodate a three-degree misalignment, self-aligning ball bearings minimize friction and frictional heat. Due to the relatively small contact angle, axial load capacities of these bearings are lower than, for example, that of angular contact bearings. 

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The bearings are capable of handling both static and dynamic misalignment. In addition, sealed, self-aligning ball bearings are resistant to dirt and other contaminants. There are many applications for self-aligning ball bearings, including mining, food processing and mass production, such as in the textile industry.

Construction of Self-Aligning Ball Bearings

A self-aligning ball bearing consists of an outer ring, an inner ring, rolling elements, a cage to house the rolling elements and a possible seal that protects the rolling elements and lubricants from contaminants. Their design allows them to compensate for a shaft and housing assembly misalignment up to three degrees. The low friction within the bearing will enable them to operate at higher speeds while generating far less heat than other bearings.

Outer ring

The outer ring of the bearings is smooth and spherical without raceways. As a result of the ring’s shape, the bearing can move slightly within itself, allowing it to adjust to misalignment.

Inner ring

The self-aligning bearing’s inner ring is formed by two raceways holding the balls and cage.

Rolling elements and cage

A cage and an inner ring hold the rolling elements of self-aligning ball bearings in place. Friction and frictional heat are low as there is a loose configuration between the balls and the inner and outer rings. Typically, the cage is made of stamped steel, reinforced glass fiber or machined brass.

Seal

Self-aligning, sealed ball bearings keep dirt and other contaminants from affecting rolling elements and
lubricants. This considerably extends the bearing’s life cycle, eliminates additional friction and reduces maintenance costs and intervals.

Advantages & Disadvantages

Ball bearings with self-aligning characteristics have many advantages over other kinds of bearings like tapered bearings, deep groove ball bearings, etc. However, the load-carrying capacity of self-aligning ball bearings is not as high as that of traditional ball bearings.

Advantages

Misalignment: Self-aligning ball bearings can counteract static and dynamic misalignment of up to
3 degrees.

Service life: These bearings offer high-speed performance and generate less heat and friction than other ball bearing types. This allows them to run cooler and extends their service life while reducing maintenance.

Light load performance: This type of bearing has low load requirements, which means they perform well even under light loads.

Low noise: Self-aligning ball bearings produce low noise levels due to the loose conformity between the rolling elements and the outer ring. This makes them especially suited for household items such as fans.

Disadvantages

Load types: The ball bearings on self-aligning ball bearings are mounted at a relatively straight angle between the inner and outer ring. This makes them suitable for handling radial loads but not axial loads.

Load amount: As self-aligning ball bearings have a small point of axial load-bearing contact, the amount of axial load they can handle is relatively small. If heavy loads are required to be carried, a spherical roller bearing, which has the same self-aligning properties, is recommended.

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Self-Aligning Bearing Installation

Adapter sleeves are typically used to mount self-aligning ball bearings. 

To properly install these bearings, follow the steps below: 

• Package with protective films that prevent outside influences from interacting with the components during transport. Ensure that these films are removed before mounting the bearing.
• Apply oil or grease to the bearing’s exterior surface.
• Use oil to lubricate the adapter.
• Open the adapter slightly and slide it onto the shaft with a spreader tool.
• Place the bearing on the adapter sleeve after the adapter is in the correct position. To bring the bearing to the right place, use a nut if the shaft has threads; if not, use a bearing pusher kit or a small mallet.
• Ensure that the bearing can rotate on the outer ring once it is in place. There should be no swiveling possible, but it should be free to rotate.
• Lock the bearing in place with a locking washer by removing the nut, placing the washer and reinstalling the nut.

Note: The inner ring of the adapter sleeve can start turning if the adapter sleeve is loose or not adequately secured in place. As a result, there may be excessive friction between the three components, damaging the shaft, the adapter and the bearing.  

Self-Aligning Bearing Selection Criteria

A self-aligning bearing’s selection is based primarily on the consideration of possible alignment problems but also the application’s rotational speed, load type, load size, tolerances and bearing dimensions.

Misalignment

Bearings with self-aligning abilities are often preferred by necessity. Self-aligning ball bearings are a
great solution when there is a possibility of shaft misalignment. Remember that most self-aligning bearings are only capable of handling misalignments of three degrees or less. Any misalignment above this would need a more customized bearing.

Speed

Compared to conventional bearings, self-aligning bearings can operate at much higher speeds. For high-speed applications, self-aligning bearings are an excellent choice. However, lubrication and bearing size are also factors that affect speed. Therefore, it is also crucial to consider the speed, type of lubrication and load requirements of your machine. The operating pace of grease lubrication is slower than oil lubrication.

Loads

A self-aligning bearing is suited for radial loads but is not suited for axial loads because of its slight contact angle. Be sure to consider this when choosing a bearing.

Seal type and lubrication

A lubrication procedure may be required if the bearing has either an open or shielded seal. Otherwise, a closed seal bearing is typically prelubricated.

Dimensions

Based on the speed requirements, the type of load, the amount of load, the shaft size and the size of the housing, select the bearing size.

• Article date: 02/12/

5 Reasons to Use Self-Aligning Ball Bearings

• Category: Product related

Maintaining efficiency and reliability is essential in many industries. This means bearings face many challenges, the most significant being misalignment issues, which can increase wear, reduce efficiency, and lead to costly downtime. Fortunately, self-aligning ball bearings have proven to be an excellent solution in these harsh conditions, offering unique benefits in terms of load handling and misalignment correction.

Self-aligning ball bearings are designed to accommodate both static and dynamic misalignment. Unlike standard bearings, they provide more flexibility and resilience, adapting to minor shifts and deflections without compromising performance. This feature is especially beneficial when bearings are used in machinery where continuous high-speed operation is required.

In this post, we’ll explore the advantages of self-aligning ball bearings and how they can improve machinery performance.

• Automatic Misalignment Correction: certain machinery can often experience shifts and minor alignment issues due to vibrations, shock loads, and temperature fluctuations. Self-aligning ball bearings are built to compensate for misalignments between the shaft and housing. This self-correcting feature reduces the risk of premature wear, decreases maintenance requirements, and ultimately extends the bearing’s lifespan.

• Superior Load Handling: Self-aligning ball bearings can withstand radial and very light axial loads, making them well-suited for applications in industries like industrial fans, agriculture, material handling, food & beverage and pulp & paper. These bearings provide optimal load distribution, reducing stress on individual components and preventing uneven wear.

• High-Speed Performance: Unlike roller bearings that use linear contact, self-aligning ball bearings rely on point contact. This feature allows them to operate efficiently at higher speeds with reduced friction, ensuring smoother, cooler operation even under strenuous conditions. The high-speed capability is vital for machinery that relies on continuous, rapid motion to maintain productivity.

• Reduced Maintenance Downtime: Regular maintenance is crucial for any industrial setup but can be costly and time-consuming. Self-aligning ball bearings offer enhanced durability, reducing the frequency and intensity of maintenance requirements. In high-demand environments, this advantage minimises downtime, enabling uninterrupted production and saving both time and operational costs.

• Enhanced Performance in Contaminated Environments: Many harsh environments, such as those in agriculture, are subject to dust, moisture, and other contaminants that can lead to corrosion and damage to mechanical parts. Self-aligning bearings are often designed with seals or shields to prevent contaminants from entering, which prolongs their operational life even in adverse conditions. Some models are also made from corrosion-resistant materials, ensuring they can withstand exposure to harmful particles or liquids.

How to Select the Right Self-Aligning Bearing

When choosing a self-aligning bearing, it’s essential to consider factors such as load type, operational speed, and environmental conditions. Here are some tips for selecting the right bearing:

• Load Capacity: Assess the weight and type of loads your machinery handles. While self-aligning ball bearings are excellent for radial loads, if your application requires high axial load capacity, it may be beneficial to combine them with other bearing types.

• Material Selection: In environments with high moisture or chemical exposure, consider bearings made from corrosion-resistant materials.

• Sealing Options: Sealed self-aligning ball bearings can be ideal in contaminated environments, preventing dirt, dust, and moisture from entering.

Conclusion

Self-aligning ball bearings are invaluable for machinery operating in challenging environments. Their automatic misalignment correction, high-speed capability, and robust load handling make them ideal for applications in industries requiring strength and efficiency. By reducing maintenance requirements and preventing premature wear, self-aligning ball bearings help keep operations running smoothly and reduce operational costs in the long term. ACORN is committed to finding the best solution for your machinery that will keep you up and running for longer; talk to our bearing specialist today about your machine's requirements.