Bearings are mechanical part with primary function of reducing friction by transmitting load, supporting and locating the shaft. There are 2 major types of bearings which are rolling bearing and journal or plain bearings. Rolling bearings have four major elements but some special bearings can miss one of the elements for some specific applications. The four major parts are rolling element, cage, inner ring and outer ring.
Rolling bearings have rolling elements while the plain bearings do not have rolling elements. The rolling bearings can either be with a ball or roller as rolling element. The ball is can only be varied by size but the roller can be varied in size and cross-section to satisfy specific requirement. The ball is used mostly when high speed is required and roller is used where high load carrying capability is of importance.
Cage refers to the component in which the rolling element are located at equidistant position so that there could be effective load distribution within the bearing in operation. The cage also function to hold lubricant for the bearings and also prevent interaction between rolling elements. They also retain the rolling elements when bearings of separable bearings are mounted or dismounted. The cage can either be polyamide, steel or brass. Some specific bearings have standard cage types that will not show in the designation while some show the cage type in their designations. Some variants are also limited to some specific cage types subject to manufacturers. Liaise with manufacturer catalog to be sure of what is available from them.
Inner ring is the component that is mostly fixed on the shaft of the driven equipment and rotates mostly with the driven equipment. In very few applications, we see the inner ring fixed but the outer ring rotates, mostly drum-like driven equipment. The part to which the rolling element contact the inner ring is called the inner raceway. The inner raceway must maintain its size and must be protected against dent as once this is affected, the life of the bearing is already getting reduced.
Outer ring is the part mostly fixed on the housing of the driven equipment. The part to which the rolling element contact the outer ring is called the outer raceway. The outer raceway must maintain its size and must be protected against dent as once this is affected, the life of the bearing is already getting reduced.
Other parts not a must are the seals or shields, grooves, lubricants and snap rings.
Most rolling bearing manufacturers name their bearings types with reference to the type of rolling elements and shape of the rolling element and shape of the raceway. Here are some of the names and physical properties that suggest its name:
|Bearing Type||Type and Shape of Rolling Element||Raceway|
|Deep Groove Ball Bearing||Ball||Deep raceway|
|Spherical Roller Bearing||Sphered roller||Inner raceway divided into 2 and 1 outer raceway|
|Angular Contact Ball Bearing||Ball||Angled raceway|
|Taper Roller Bearing||Roller||Inner and outer raceway tapered|
The ball makes a point contact with the raceway and makes it suitable for hight speed applications. The roller makes a line contact with the raceway and makes it suitable for high load applications. The most common type of bearing is the deep groove bearing in different sizes to miniature bearings in most high-speed applications.