Self-Aligning Bearing Guide And Overview

Figure 1: Self-aligning bearing

View Details

Self-aligning ball bearings are ideal for applications with misalignment issues between the shaft and housing. Due to their design, self-aligning ball bearings can accommodate up to 3° of misalignment without increasing the amount of friction and frictional heat produced. However, as the contact angle is relatively small on these bearings, the axial load capacity is not as high as, for example, angular contact bearings. These bearings can handle both static and dynamic misalignments. A sealed self-aligning ball bearing also protects it from dirt and other contaminants. Self-aligning ball bearing applications can be found in various industries, such as mining, food processing, and mass production use, such as the textile industry.

Table of contents

• Self-aligning ball bearings construction
• Advantages and disadvantages
• Mounting a self-aligning bearing
• Selection criteria

Self-aligning ball bearings construction

Self-aligning ball bearings consist of an outer ring, an inner ring, rolling elements, a cage to house the rolling elements, and seals that protect the balls from contaminants and other dirt. Due to their design, these elements make it possible for self-aligning bearings to counteract any static or dynamic misalignment of a shaft and housing assembly up to 3°. They also generate far less heat than other bearings due to the low friction within the bearing, allowing them to run cooler than other bearings at higher speeds. Self-aligning bearings work by utilizing a design with two rows of balls or rollers separated by a spherical raceway.

• Outer ring: The outer ring of the bearings has a smooth spherical shape without raceways. The shape of the outer ring allows for slight movement within the bearing, which in turn allows the bearing to self-align.
• Inner ring: The inner ring of the self-aligning bearing has two raceways that keep the balls and cage in place.
• Rolling elements and cage: The rolling elements on self-aligning ball bearings are kept in place by the cage and the inner ring. As there is a loose configuration between the balls and the inner and outer ring, friction and frictional heat are very low. The cage is typically stamped steel, PA66, reinforced glass fiber, or machined brass.
• Seal: A sealed self-aligning ball bearing ensures dirt and other contaminants don't affect the bearing rolling elements.

Advantages and disadvantages

There are many advantages of self-aligning ball bearings over other bearing types, such as tapered bearings, deep groove ball bearings, and other ball bearing types. However, self-aligning ball bearings do not perform as strongly in terms of load-carrying capacity.

Advantages

• Misalignment: Self-aligning ball bearings can counteract static and dynamic misalignment of up to 3°.
• Service life: These bearings offer excellent high-speed performance and generate far 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 very low load requirements, which means they perform excellent, even under light loads.
• Low noise: Self-aligning ball bearings produce low noise levels due to the loose conformity between balls and the outer ring. This makes them especially suited for use in household items such as fans and air conditioning units.

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 means that the load types the bearing can handle is radial, with little axial load carrying capacity.
• Load amount: As ball bearings have a small point of load-bearing contact, the amount of load this type of bearing can handle is relatively small.

Mounting a self-aligning bearing

Most self-aligning ball bearings will be mounted using an adapter sleeve. In the below steps, we explain this procedure:

1. Bearings often come with a protective film that protects the components from outside influences during transport. Make sure to remove this film before mounting the bearing
2. Oil the exterior surface of the bearing with oil or grease.
3. Apply oil to the adapter.
4. Open the adapter slightly with the help of a screwdriver and slide it in place on the shaft.
5. Once the adapter is in the correct position, position the bearing on the adapter sleeve. If the shaft has threads, it will help to use a nut to bring the bearing in the correct place; if not, use a bearing pusher kit or a small mallet.
6. Once the bearing is in place, test the rotation of the bearing on the outer ring. It should be able to rotate freely, but not swivel.
7. Lock the bearing in place with a locking washer by first removing the nut, placing the washer in place, and putting the nut back again.

Note: If the adapter sleeve is loose or not properly secured in place, the inner ring can start turning on the adapter sleeve. This causes excessive friction between the three components and can damage the shaft, adapter, and bearing.

Figure 2: Mounting a self-aligned bearing ball-bearing-self-align.jpg

Selection criteria

When selecting self-aligning bearings, the primary considerations revolve around any possible alignment problems, rotational speed, load type, load size, tolerances, and bearing dimensions:

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. 

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.

With competitive price and timely delivery, Shangyou sincerely hope to be your supplier and partner.

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.

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.

Want more information on self aligning ball bearings supplier(ar,pl,fa)? Feel free to contact us.