An Outer Ring:- This is the larger of the two rings and, like its counterpart
the inner ring, its name is derived from the position it holds. Conversely,
there is a groove on its inside diameter to form a pathway for the balls.
This surface also has the same high precision finish of the inner ring. The
outer ring is normally placed into a housing and is usually held stationery.
These are the rolling elements that separate the inner and
outer ring and permit the bearing to rotate with minimal friction. The ball
radius is slightly smaller than the grooved ball track on the inner and outer
rings. This allows the balls to contact the rings at a single point,
appropriately called point contact. Ball dimensions are controlled to
very tight tolerances. Ball roundness, size variations, and surface finish are
very important attributes and are controlled to a micro inch level
(1 micro inch
= 1/1,000,000th, or one-millionth of an inch).
Rolling elements can be either Balls, Cylindrical Rollers, Spherical Rollers, Tapered Rollers and Oil in case of Journal type of Bearings.
The main purpose of the cage is to separate the balls,
maintaining an even and consistent spacing, to accurately guide the balls in the
paths, or raceways, during rotation, and to prevent the balls from
Cage may be of Steel, Brass, Bronze, or Phenolic composition, depending upon the type and application of the bearings.
The parts of a Bearing in general is illustrated in the figure.
Bearings are designed in such a way that they offer following advantages:-
- Low Friction--Particularly low starting friction.
- The ability to support both radial and thrust load and high speeds of rotation.
- Accurate performance under changing load and speed.
- High Load Carrying capacity
- Operating ability under extreme conditions of speed and performance.
- Practically no wear in running.
- Simple methods of Lubrication.
- Inherently Precision Mechanisms.
The above advantages clearly justify the ubiquitous presence of Bearings in our life.