Types of Bearings, Their Classification and Applications

Bearings are used to reduce friction when there is relative motion between two parts like shaft and housing. There are several types of bearings in the market out of which two major groups of bearings are,

Sliding contact bearings are also called journal bearings or bush bearings. Rolling contact bearings are also called as antifriction bearings or simply ball bearings.

1. The bearing ensures free rotation of the shaft or the axle with minimum friction.
2. The bearing supports the shaft or the axle and holds it in the correct position.
3. The bearing takes up the forces that act on the shaft or the axle and transmits them to the frame or the foundation.

Types of Bearings

There are 7 different types of bearings

1. Ball Bearings
2. Roller Bearings
3. Linear Bearings
4. Jewel Bearings
5. Plain Bearings
6. Fluid Bearings
7. Magnetic Bearings

Ball Bearings

Ball bearings are the most common types of bearings. A ball bearing is a bearing in which the parts are separated by a ring of small freely rotating metal balls which reduce friction.

A ball bearing consists of metal balls located between races. These balls are kept in position within the assembly with the help of a cage.

The balls and inner races are free to rotate while the outer race is stationary. Shaft or shaft-like round objects are fitted inside the inner race while the outer race is fitted in an object.

Roller Bearings

Linear Bearings

A linear bearing is a bearing that provides free motion in one direction. It contains balls or rollers between two races which are used to give linear motion between two components.

Types of Linear Bearings

• Flat Ball cage
• Ball bushing
• Needle roller cage
• Ball spline
• Flat roller cage
•  Linear roller

Jewel Bearings

Jewel bearings are used in applications like watches where there is a small size shaft. These shafts are very small in size and have precision work.

Plain Bearings

Plain bearings are the simplest types of bearings. It consists only of a bearing surface and does not contain any rolling element.

Fluid Bearings

Fluid bearings also known as hydrodynamic bearings are the bearings in which the load is supported by a thin layer of pressurized fluid between the bearing surfaces.

Magnetic Bearings

A magnetic bearing is a bearing that supports a load using magnetic levitation.

There are two types of magnetic bearings

1. Active bearing
2. Passive bearing

Active bearing uses an electromagnet, which activates as the shaft moves out of its desired location. Using electromagnetic levitation, bearing action is achieved.

The passive bearing makes use of a permanent magnet. These are difficult to design.

Bearings Classification

Bearings are classified in different ways. Depending upon the type of load, bearings are classified into two categories.

1. Radial bearings
2. Thrust bearings

A radial bearing supports the load, which is perpendicular to the axis of the shaft. According to Springer, Radial bearings refer to bearings that support primarily radial loads. Typical examples of radial bearings are deep groove ball bearings, cylindrical roller bearings, and needle bearings.

A thrust bearing also known as axial bearings supports the load which is parallel to the axis of the shaft.

Radial and Thrust bearing

The type of lubrication means the extent to which the contacting surfaces are separated in a shaft bearing combination. This classification contains

• Thin-film lubrication
• Thick film lubrication
• Boundary lubrication

The most important criterion to classify the bearings is the type of friction between the shaft and the bearing surface.

Depending upon the type of friction, bearings are classified into two main groups

1. Sliding contact bearing.
2. Rolling contact bearing.

Sliding Contact Bearing

Sliding contact bearings are also called plain bearings, journal bearings, or sleeve bearings. In this case, the surface of the shaft slides over the surface of the bush resulting in friction and wear. In order to reduce the friction, these two surfaces are separated by a film of lubricating oil. The bush is made of special bearing material like white metal or bronze.

• Centrifugal pumps
• Large size electric motors
• Crankshaft bearings in petrol and diesel engines
• Concrete mixer, marine installations, and rope conveyor.

Rolling contact bearings are also called anti-friction bearings or simply ball bearings. Rolling elements such as balls or rollers are introduced between the surfaces that are in relative motion. In this type of bearing, sliding friction is replaced by rolling friction.

Depending upon the type of rolling element, bearings are classified as:

• Deep groove Ball-bearing
• Cylindrical roller bearing
• Angular Contact bearing
• Self-aligning bearing
• Taper roller bearing
• Thrust ball bearing

• Automobile front and rear axles
• Gearboxes
• Machine tool spindles
• Small size electric motors
• Rope sheaves, crane hook, and hoisting drum.