Angular contact ball bearings, also known as spindle ball bearings, consist of an inner ring, outer ring, ball, and a cage to contain and separate the ball. Angular contact ball bearings can support an axial load, but cannot be used by a single bearing because of their angle. They must be used in combinations or in pairs.
An angular contact ball bearing uses axially asymmetric races. An axial load passes in a straight line through the bearing, whereas a radial load takes an oblique path that tends to want to separate the races axially. So the angle of contact on the inner race is the same as that on the outer race. Angular contact bearings better support “combined loads” (loading in both the radial and axial directions) and the contact angle of the bearing should be matched to the relative proportions of each. The larger the contact angle (typically in the range 10 to 45 degrees), the higher the axial load supported, but the lower the radial load. In high speed applications, such as turbines, jet engines, and dentistry equipment, the centrifugal forces generated by the balls changes the contact angle at the inner and outer race. Ceramics such as silicon nitride are now regularly used in such applications due to their low density (40% of steel). These materials significantly reduce centrifugal force and function well in high temperature environments. They also tend to wear in a similar way to bearing steel—rather than cracking or shattering like glass or porcelain.
Most bicycles use angular-contact bearings in the headsets because the forces on these bearings are in both the radial and axial direction.
Angular contact ball bearings have raceways in the inner and outer rings that are displaced with respect to each other in the direction of the bearing axis. This means that they are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.
The axial load carrying capacity of angular contact ball bearings increases with increasing contact angle. The contact angle α is defined as the angle between the line joining the points of contact of the ball and the raceways in the radial plane, along which the load is transmitted from one raceway to another, and a line perpendicular to the bearing axis (fig).
SKF angular contact ball bearings are produced in a wide variety of designs and sizes. Those commonly used and included in this catalogue are
– single row angular contact ball bearings
– double row angular contact ball bearings
– four-point contact ball bearings
Angular contact ball bearings are classified with different accuracy and tolerance ranges for ball bearings on the ABEC bearing rating scale. A higher ABEC number indicates that the bearing tolerances are tighter. When searching for your angular contact bearing, it is important to consider aspects like operation specifics and dimensions.
Operating Specifics for Angular Contact Ball Bearings
- Static radial load: the maximum radial load the bearing can withstand without succumbing to the pressure
- Dynamic radial load (calculated constant radial load): the amount of load a set of similar bearings with fixed outer rings can withstand against a rating life of one million revolutions of the inner ring
- Rated speed: Grease lubrication gives a lower rated speed for bearings as compared to a bearing with oil lubrication.
Dimensions for Angular Contact Ball Bearings
- Design units of angular contact bearings can be in either inches or metric units
- Outside diameters include housing for housed units but exclude the flange for flanged bearings
- Outer ring width
The most common types of angular ball bearing include four point contact ball bearings, singular row, and double row angular contact ball bearings. Angular contact bearings have different kinds and styles of shielding and seals, which essentially retain lubricant to provide protection against contamination. In this type of bearing, there are different types of seals and shields used, including single seal, double seal, single shield, and double shield. When compared to shields, seals provide better lubricant coverage and containment, but have a reduced maximum speed capability.
There are a variety of materials used in the construction of the angular contact bearing, including stainless steel, ceramic, and plastic. This type of ball bearing can also be plated. The materials that are commonly used to plate these bearings include chrome and cadmium.