Industrial machines consist of small parts. In general, all types of machines have a supporting device for rotating shafts. This supporting device is called a bearing. The bearings are most widely used all over the world. They are installed to assist, guide, and limit the rotating parts of a vehicle. The bearings are static elements that carry the load. They reduce the friction between the moving parts. This article mainly explains the bearing types, function, and some other aspects.
What is a Bearing?
The word “bearing” is derived from the verb “to bear.” The bearing is a mechanical element that limits relative movement and reduces friction between rotating components. Bearings allow one part of the system to support another part. They have a high ability to bear heavy loads.
The main function of the bearing is to transmit motions, such as it supports and guides the parts that rotate relative to each other.
The bearings are the most important elements of the vehicle. According to the application’s nature, there are multiple types of bearings. They deliver the required direction to a specific part.
The plain bearing is one of the most famous types of bearings. It uses a frictional contact surface with a lubricant such as graphite or oil. It can simply be a bearing surface that the shaft passes through its hole, a plane surface that supports another shaft (not a separate device in these cases), or separable sleeve form (discrete type), or a layer of supporting metal.
With sufficient lubrication, plain bearings generally deliver friction at the lowest cost, extend the service life of the system, and have excellent precision. Therefore, these types are most commonly utilized.
However, you must select bearings according to the nature of the application. The best suitable bearings improve machine efficiency, weight, size, service life, accuracy, operating speed, reliability, and initial and operating costs.
Types of Bearings
There are different types of bearings based on their working principles, materials, lubrication, shapes, etc. The following are the major types of bearings:
- Ball Bearing
- Roller Bearing
- Linear Bearing
- Bush Bearing
- Thrust Bearing
- Foot Step Bearing
- Anti-friction or Rolling Contact Bearing
- Plain Bearing
- Fluid Bearing
- Magnetic Bearing
- Jewel Bearing
- Flexure Bearing
1) Ball Bearing
The ball bearing is one of the most famous types of bearings. It has a small metal ball. This ball is located in between two metal rings. These metal rings are known as the races.
The ball is held in place by an assembly known as a cage. During the working of the ball bearings, there is a small contact area between the race and the ball. These bearings have limited bearing ability and generate less friction torque.
The ball bearing usually contains the following two races.
- The exterior race is fixed.
- The inner race can move freely. The machine shaft is inserted into the inner race.
The ball bearings are most commonly used for printing, wind energy, medical, material handling, machine tool, food processing, and agricultural applications.
Advantages and Disadvantages of Ball Bearings
| Advantages | Disadvantages |
|---|---|
| They produce very little resistance. | They are a little bit noisy. |
| You can easily replace the parts of these bearings. | These bearings may damage or break due to shocks. |
| They have low costs. | |
| They have the ability to handle high loads. | |
| These bearings have a long service life. |
2) Roller Bearings
The roller bearings are designed to sustain the precise alignment of each component for a long time. They also have the ability to withstand heavy transient loads. Therefore, they are ideal for machines that need to be started and stopped frequently. These bearings have a cylindrical rolling element instead of a ball.
The balls make point contact with their races while the rolling action of the bearings generates line contact. The roller bearing has a very high load-carry ability.
Advantages and Disadvantages of Roller Bearings
| Advantages | Disadvantages |
|---|---|
| They are easy to maintain. | They generate extreme noise |
| Low friction. | They are very expensive. |
| They have the ability to bear a heavy load. |
3) Linear Bearings
Linear bearings have a rolling or ball element. This rolling or ball element is installed between two races. These types of bearings are used to impart linear motion to the moving part of the machinery.
They reduce friction between the moving parts of the system where motion works in straight lines. The drawer of a cupboard and sliding doors are the simplest examples of linear bearings.
Linear bearings have the ability to control the speed more precisely than other types of bearings. They have high stiffness and the ability to bear heavy loads. They also don’t need maintenance and lubrication. These bearings are ideal for food processing equipment and packaging machines.
Advantages and Disadvantages of Linear Bearings
| Advantages | Disadvantages |
|---|---|
| They don’t require lubrication. | They have a small carrying capacity. |
| They don’t need maintenance. | These bearings require special attention. |
| These bearings control the speed more excellently than other bearings. |
4) Bush Bearings
These bearings have a bronze or brass bushing and a cast iron bearing housing. In this type of bearing, the bottom plate of the bearing housing has holes to hold the bearing in place.
A counterboring oil hole is located at the top of the bearing. There is a bush that is installed to lubricate the shaft and bushing. These bearings are ideal for shafts that turn at a low speed under light loads. This type of solid bearing allows you to slide the shaft in and out gently.
The bush bearings have a rubbing action between the bearing’s internal surface and the external surface of the shaft. The presence of a lubricating oil film minimizes the resulting friction. The oil ring is considered the most efficient and safest type for linear shafts under normal operating conditions.
Advantages of Bush Bearings
- Reduction of the machinery running cost.
- The use of the bush bearings also reduces the operating costs of the machine.
5) Thrust Bearings
In the case of axial or thrust bearings, the bearing pressure is axial. It has a horizontal or vertical shaft axis. Thrust bearings are called roller bearings when the shaft axis is horizontal. Thrust bearings are called footstep bearings when the shaft axis is vertical.
6) Footstep Bearings
This type of bearing is an ideal type to support a vertical shaft. These bearings have a bronze bushing and a cast-iron block. The shaft’s lower edge inserts into a steel disc. This steel disc contains concave seating.
The footstep bearing prevents the disc from rotating along the shaft by inserting the pin partway in the disc and partway in the block. By fitting into the neck below the collar, it prevents the bush from turning with the shaft.
In these bearings, effective lubrication is very hard to achieve. The footstep bearings are commonly used for low-speed shafts that carry a light load. Vertical shafts are not common in ordinary power transmission. The footstep bearings are most commonly used in textile machines and machine tool rotary tables.
Advantages and Disadvantages of Foot Step Bearings
| Advantages | Disadvantages |
|---|---|
| They are ideal to support vertical shafts with axial load. | They can’t be lubricated efficiently. |
| They have uneven wear on the bottom disc. |
7) Anti-friction or Rolling Contact Bearings
The rolling contact bearings can easily roll on similar surfaces like sliding bearings. This method uses hard chrome-plated steel rollers or balls to move in a specially designed cage to give low friction loss bearings.
This bearing has a purely rolling movement between the bearing surface and the shaft. This is because sliding friction is much higher than rolling friction.
These types of bearings have lower starting friction which can also be achieved while driving. Therefore, the rolling contact bearings are ideal for machines that need to be started, stopped, and restarted frequently.
Advantages and Disadvantages of Rolling Contact Bearings
| Advantages | Disadvantages |
|---|---|
| They provide lower starting friction. | This bearing has a high initial cost. |
| They provide more accuracy in shaft alignment. | These bearings have complex housing designs. |
| These bearings have low maintenance costs. | |
| They don’t need lubrication during operation. |
8) Plain Bearings
It is one of the simplest types of bearings. It contains a bearing surface. However, it doesn’t contain a rolling element. These bearings are most commonly used for oscillating, reciprocating, sliding, and rotational movements.
In these bearings, the journal slides in the bearing while the bearing itself remains stationary. They have a sleeve attached to the shaft and fit into the holes. They have a low weight, compact design, and lower cost than other types of bearings. These types also have high load-carrying ability.
Advantages and Disadvantages of Plain Bearings
| Advantages | Disadvantages |
|---|---|
| They have lighter weight. | They provide high friction during the transient process (especially during startup). |
| They have low cost | The plain bearing requires more axial area. |
| The parts of the plain bearing have a long fatigue-free service life. | The use of friction-resistant materials in their manufacturing is essential. |
| They generate low operational noise. | |
| They require less radial space. | |
| They are easy to install. | |
| These bearings use for higher rotational speeds. |
9) Fluid Bearings
These types of bearings highly depend on the compressed gas or liquid to carry loads and remove friction. Fluid bearings are employed in place of metal bearings.
In addition to high levels of vibration and noise, the fluid bearings use for machines that operate at high loads and speeds. They have a high initial cost and long service life in adverse conditions.
10) Magnetic Bearing
These types of bearings use the magnetic levitation principle to hold the air in the shaft center as there is no physical contact. The magnetic bearing does not wear out and limits the maximum relative movement it can control.
These bearings also offer some variations in the design of the shaft due to that they can automatically adjust the shaft position based on the center of mass. They provide multiple benefits for a variety of applications, such as high-speed turbines, centrifuges, and compressors.
11) Jewel Bearing
The jewel bearing has a very similar design to a plain bearing, but jewel bearings have jewel-lined spindle holes instead of a metal spindle.
The diameter of the holes is a little bit more than the shaft diameter. These holes usually have a ring-shaped design. Synthetic ruby, maybe synthetic sapphire, or mineral corundum is used to manufacture the jewels.
The jewel bearings are most commonly used in different industrial applications where dimensional accuracy, low friction, and long equipment service life are important. Jewelry bearings are usually employed in mechanical watches.
12) Flexure Bearings
These types of bearings are usually employed to maintain degrees of freedom at one or more angles. They are also known as part of the compliance mechanism. For applications that need angular compliance, these bearings work similarly to traditional bearings or hinges.
The main advantages of the flexure bearings are that they don’t need lubrication and give very small friction. They have simple designs and low costs. They are small, low weight, and easy to service with special equipment.
Applications of Bearings
The bearings are most commonly used for the following applications:
- Commercial blenders
- Motorcycles
- Dental hand tools
- Anemometer
- Airplanes
- Electric generators
- Tractors
- Electric motors
- Aerospace wing actuators
- Harvesters
- ATMs & Card Readers
- Vehicle engines
- Bicycles
- Aviation cargo systems
FAQ Section
What is the Function of the Bearing?
The primary function of a bearing is to prevent the rotating metal parts from making direct metal-to-metal contact. In this way, it averts heat generation, friction, and the resultant wear and tear. Furthermore, bearings also play a vital role in reducing energy consumption by substituting high-friction sliding motion with efficient rolling.
What are the types of bearings?
- Flexure Bearings
- Roller Bearings
- Fluid Bearings
- Linear Bearings
- Foot Step Bearings
- Bush Bearings
- Thrust Bearings
- Jewel Bearings
- Anti-friction or Rolling Contact Bearings
- Plain Bearings
- Magnetic Bearings
- Ball Bearings
Where are bearings used?
The bearings are most commonly used for different applications such as photocopiers, vehicle engines, DVD players, bicycles, blenders, airplanes, and skateboards.
What are bearings made of?
The bearings are made of different materials such as plastic, ceramics, stainless steel, or high-carbon chromium steel. However, high-carbon chromium steel is most commonly used to construct the bearings.