Self-aligning ball bearings are recommended for applications where shaft and housing alignment is difficult or where the shaft may bend, such as propeller shafts. The outer ring has a spherical raceway whose center of curvature coincides with that of the bearing, allowing the axis of the inner ring, balls and cage to rotate freely about the center of the bearing.
This type usually uses a stamped steel cage. Self-aligning ball bearings have a low axial load capacity due to the small contact angle. Allowable dynamic deflection is approximately 0.07 to 0.12 radians (4 to 7 degrees) under normal load.
Self-aligning ball bearings have two rows of balls, a common spherical raceway on the outer ring and two deep uninterrupted raceway grooves on the inner ring. They can be used open or sealed. These bearings are insensitive to angular misalignment of the shaft relative to the housing, which may be caused, for example, by shaft deflection.
Self-aligning ball bearings are ideal for applications where misalignment between the shaft and housing is an issue. Due to their design, self-aligning ball bearings can tolerate misalignments of up to 3° without increasing the amount of friction and generating frictional heat. However, due to the relatively small contact angle of these bearings, the axial load carrying capacity is not as high as that of angular contact bearings. Self-aligning ball bearings can handle static and dynamic misalignment. Sealed self-aligning ball bearings also protect it from dust and other contaminants. Self-aligning ball bearings are used in many different fields such as gearboxes, mining, food processing and mass production applications such as the textile industry.
Self-aligning ball bearing structure
Outer ring: The outer ring of the bearing is a smooth spherical surface without a raceway. The shape of the outer ring allows slight movement within the bearing, allowing the bearing to self-align.Inner Ring: The inner ring of a 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 fixed by cages and inner rings. Due to the loose structure between the balls and the inner and outer rings, friction and frictional heat are very low. Cages are usually made of stamped steel, PA66, fiberglass reinforced or machined brass.
Sealed: Sealed self-aligning ball bearings ensure that dust and other contaminants do not affect the bearing rolling elements.
Self-aligning ball bearings have many advantages over other bearing types such as tapered bearings, deep groove ball bearings and other ball bearing types. However, self-aligning ball bearings perform poorly in terms of load carrying capacity.
Misalignment: Self-aligning ball bearings can compensate for static and dynamic misalignment of up to 3°.
Longevity: These bearings have excellent high-speed performance and generate much less heat and friction than other types of ball bearings. This allows them to run cooler and extend their life with less maintenance.
Light Load Performance: These bearings have very low load requirements, which means they perform well even under light loads.
Low noise: Due to the loose fit between the balls and the outer ring, self-aligning ball bearings produce low noise levels. This makes them especially suitable for use in household items such as fans and air conditioning units.
Load type: The ball bearing on the self-aligning ball bearing is installed at a relative right angle between the inner ring and the outer ring. This means that the type of load the bearing can carry is radial, with little axial load carrying capacity.
Load capacity: Due to the small load contact points of ball bearings, the load capacity that this type of bearing can carry is relatively small.
When selecting a self-aligning bearing, the main considerations revolve around any possible alignment issues, speed, load type, load magnitude, tolerances and bearing size:
Misalignment: Self-aligning bearing selection often comes down to necessity. Self-aligning ball bearings are the clear choice when operating with the possibility of shaft misalignment. Remember that most self-aligning bearings can handle misalignments of up to 3°. Any value above this will require a unique design.
Speed: Self-aligning bearings operate significantly faster than most conventional bearings. If you need high-speed bearings, self-aligning bearings are a good choice. However, the speed also depends on the type of lubrication and the size of the bearing. Therefore, it is also important to consider your operating speed requirements, the type of lubrication required, and the required load capacity.
Loads: Self-aligning bearings are great for radial loads, but less so for axial loads due to their smaller contact angles. Keep this in mind when selecting bearings.
Lubrication and seal types: In general, there are three possible lubrication options: relubrication, usually with open or shielded seals; prelubrication, usually with closed seals; or solid lubrication, usually with closed seals.
Size: Select bearing size based on speed requirements, load type, load capacity, shaft size and housing size
The size and width of these bearings can also vary according to their use and application. These bearings are mostly used for general purpose. Self-aligning ball bearings can be open or sealed. The design of the bearings allows them to be used in difficult applications. They are commonly used in textile mining, agriculture, heavy machinery, power machinery and medical equipment. Stamped steel, bronze and polyamide cages are commonly used. Due to the small contact angle, the axial capacity is also small. Available with cylindrical and tapered bores, misalignment is permitted from 4 to 7 degrees under normal load. Self-aligning ball bearings also have three series, namely 1200, 1300 and 2200. As a premier ball bearing distributor, AUB offers an extensive range of ball bearings to suit almost any application.