This website uses cookies for a better browsing experience.
Please read and agree to the “Terms of Use”.
If you wish to change your cookie settings, click on “Settings” to customize them.

Our website may store information on your browser or retrieve information from your browser. This information is about you, your preferences, traffic analysis, or your device and is used, in most cases, to make the site function as you expect. To respect your right to privacy, you can choose not to allow cookies. Please note that some cookies are necessary for the proper functioning of the website and their use cannot be stopped on our system.


  • This cookie is necessary for the site to function properly and cannot be stopped in the user's system.
Contact Us
Select Your Country
It all started with a small wooden bearing.
PRODUCTS

What Are Bearings? The Types, Roles, Mechanisms, Structures, History, and Selection Methods of Bearings

This article provides a comprehensive overview on the basic role of bearings, the various types of bearings available and how to select them, and the history of bearings.

To consult us on ways to use plain bearings or if you are considering incorporating plain bearings in your products, please Contact Us at Oiles Corporation.
As a leading manufacturer of oil-less bearings with the world’s number one market share in bearings for a number of components (and applications), such as steering systems, we will draw on our advanced technology and abundant know-how to suggest the appropriate bearing for you.

Oiles Corporation

1. What Are Bearings?

Bearings are important elements of machinery, which are used to bear a component such as a shaft.
This section describes the features of bearings and their history.

(1) Features and Roles of Bearings

Bearings are components that support smooth operation by reducing the frictional resistance of machine parts that perform motion such as rotating motion or reciprocating motion. By supporting the shafts of a machine, bearings reduce frictional resistance and thereby increase energy efficiency. They also keep the shafts of a machine in the correct position and help protect parts subject to strong forces.
Bearings are incorporated and used in all kinds of machinery, like the engines and wheels of vehicles such as aircraft and automobiles and the gears and motors of industrial machinery and household appliances.

(2) History of Bearings

Murals from Ancient Egypt depict the transport of heavy stones for building pyramids and palaces. The stones were smoothly moved by sliding them across a lubricated surface to reduce frictional resistance. This is the same function as a bearing.

Source: History of Tribology, published by Kogyo Chosakai Publishing Co., Ltd.

In the Renaissance, the polymath genius Leonardo da Vinci left behind a sketch depicting the basic design of a bearing. His sketch featured a rotary device using balls as a rolling element to reduce frictional resistance, which is the same basic principle as a contemporary bearing.

From the 16th century, western countries created bearings with metal balls and rollers, which were used in gun carriages and water wheels.

The first true modern bearings are said to be those developed for horse carriages after the industrial revolution that occurred in England in the late 18th century.

In the mid-19th century, plain bearings using wood called lignum vitae were used in the screws for ships.

Bearings were first manufactured in Japan at the beginning of the 20th century. This led to the spread of bearing manufacturing technology throughout the country.

The next major event in the history of bearings occurred in the year 1932. The founder of Oiles Corporation, Sozo Kawasaki, patented a manufacturing method for impregnating oil in a wooden bearing. These wooden oil-impregnated bearings were first sold in Japan as oil-less bearings. This was the beginning of the history of bearings at Oiles Corporation.

2. Types of Bearings

Bearings are generally categorized as either plain bearings or rolling bearings, which are further divided into various types. This section describes the features of the various types of bearings in more detail.

(1) Plain Bearings

Plain bearings reduce frictional resistance by interposing a lubricating coating between the shaft and the bearing or forming a bearing surface using a material with low frictional resistance. Plain bearings are generally divided into the following three types.

i. Oil-lubricated Type

Oil-lubricated type plain bearings reduce frictional resistance by supplying lubricating oil. The existence of lubricating oil maintains smooth movement.

ii. Self-lubricating Type

Self-lubricating type plain bearings include oil-impregnated bearings and solid lubricant bearings (as well as some self-lubricating plain bearings that count as both). Oil-impregnated bearings contain oil inside, and gradually release that oil during use to form a lubricating coating. Solid lubricant bearings form a lubricating coating using a solid lubricant embedded in the bearing, or the material of the bearing itself reduces wear because it has low frictional resistance. Self-lubricating type bearings can be used with minimal maintenance, without the need for lubrication. The majority of Oiles Corporation products are self-lubricating type bearings.
Oiles Bearings

iii. Special Type

Special types of plain bearings include air bearings and magnetic bearings. These bearings float a shaft with air or magnetism to provide operation with almost zero friction. They are used in machinery that requires particularly high precision, such as semiconductor manufacturing equipment and machine tools for the manufacturing of optical components.
Oiles Corporation products include Oiles Air Bearings, a special type of air bearing, which are mostly used in the semiconductor industry due to their superior rotational stability and high rigidity.​
Oiles Air Bearings (Static Pressure Air Bearings)

Details on the types of plain bearings and their advantages and disadvantages are described in a separate article. Refer to it as required.
What are plain bearings? Types, advantages, and disadvantages of plain bearings and their differences from rolling bearings

(2) Rolling Bearings

Rolling bearings reduce frictional resistance by using balls or rollers between the shaft and bearing. Common types of rolling bearings and their features are indicated below.

Type Ball Bearings Roller Bearings Needle Roller Bearings
Rolling element Ball Roller Needle roller
Features Used in a wide range of applications Suitable for higher loads than ball bearings Suitable for high loads and compact spaces
Main uses
  • Automobile wheels
  • Household appliances
  • Railway cars
  • Farming equipment
  • Large motors
  • Automobile transmissions
  • Aircraft engines

3. Structure and Mechanism of Bearings

This section describes the structure of plain bearings and rolling bearings.

(1) Structure and Mechanism of Plain Bearings

Because plain bearings support the loaded shaft across its entire surface, they generally have better load capacity, impact resistance, and foreign matter resistance than rolling bearings. They also reduce frictional resistance by generating a lubricating coating (consisting of a substance such as oil or air) between the shaft and the bearing. Thus, a feature of plain bearings is that they allow a shaft to rotate while reducing frictional resistance through the action of a lubricating coating.

The video below describes the structure of a plain bearing, using an Oiles Bearing as an example.
https://www.oiles.co.jp/files/bearing_about01.mp4

(2) Structure and Mechanism of Rolling Bearings

A rolling bearing contains rolling elements (balls or rollers) between the inner ring and outer ring. The inner ring is attached to the shaft, and the outer ring is attached to a fixed housing. The rolling elements are used to reduce frictional resistance between the shaft and bearing.

The role of each component of a rolling bearing is indicated below.

Name Role
Outer ring The outer ring of the bearing, which is fixed to the outer structure.
Rolling element The component that supports the shaft as a rolling element.
Retainer The component that supports the rolling element to ensure it remains in an appropriate position.
Inner ring The inner ring of the bearing, which is attached to the rotating shaft.

4. Example Uses of Bearings

Bearings are used in a wide range of machinery and other equipment to reduce frictional resistance and make rotation and motion smoother. This section describes specific examples of using plain bearings and rolling bearings.

(1) Typical Uses of Plain Bearings (Hydroelectric Power Generation, Robotics, Automobiles, etc.)

Plain bearings are often used in situations that particularly require load-bearing capacity, impact resistance, and resistance to foreign matter. For example, Oiles Bearings, which are a type of plain bearing, are used in a wide range of industries, such as the automobile, hydroelectric power generation, water and sewage, food machinery, robotics, and semiconductor industries, as indicated in the table below.

[Example Uses of Plain Bearings]

Automobiles
Hydroelectric power generation
Water and sewage
Food machinery
Robotics
Semiconductor manufacturing equipment

In Oiles Bearing Case Studies, you can see detailed examples of where and how our products are utilized. We also recommend the following video that showcases some everyday examples of bearing uses.
https://www.oiles.co.jp/files/bearing_about02.mp4

(2) Typical Uses of Rolling Bearings (Automobiles, Railways, Aircraft, etc.)

Due to their high versatility, rolling bearings are used in a wide range of applications, such as automobiles and motorcycles, railways, aircraft, and wind power generation.
For example, motorcycles incorporate 20 to 30 bearings, mostly in their engines and transmissions, and automobiles incorporate as many as 100 to 150 bearings.

5. How to Select Bearings

The appropriate type of bearing to select depends on the intended use and usage environment. This section describes the selection method for plain bearings and rolling bearings.

(1) How to Select a Plain Bearing

First, let’s take a look at the six steps for selecting a plain bearing.

i. Determining the Overall Layout

When determining the overall layout for machinery or other equipment, decide approximate values for the inner diameter, outer diameter, and length of the plain bearing, as well as the expected material for the mating shaft and the lubrication method.

ii. Checking the Environmental Conditions/Design Requirements

Next, check the design requirements and the conditions of the environment where the plain bearing will be used.
The suitable material for the plain bearing depends on factors such as the temperature (whether the bearing will be used at room temperature, low temperature, or high temperature) and the medium (whether the bearing will be used in air, water, or a chemical solution), as stress relaxation will occur due to the environmental conditions.
See information about stress relaxation here

iii. Considering the Usage Environment

Consider the specific usage environment to determine the durability and performance required for the bearing.

  • Check the allowed P, V, and PV values, as well as the form/state of motion, frequency of use, and whether there is lubrication.
    P value: The surface pressure P is the value derived by dividing the maximum load (W) on the bearing by the projected area (φd × L) of the bearing.
    V value: The velocity V is the relative velocity between the mate and the bearing.
    PV value: The PV value, which is the product of the surface area P and the velocity V, is another important factor in the selection of bearings.
    See the programs for calculating the P and V values here
  • Consider the environmental conditions (for special environments in particular), temperature conditions, and factors such as corrosion resistance, chemical resistance, and resistance to the infiltration of foreign matter.
  • Consider factors such as dynamic load, static load, impact load, static stress, and fracture strength.

iv. Considering the Form Design, Detailed Design, and Standard Products

Design the form and other details, and consider whether standard products can be used.

  • Consider the material, strength, rigidity, and precision of the housing. Evaluate the material, roughness, hardness, surface treatment, precision, and foreign matter prevention measures of the mating shaft.
  • Evaluate the precision, interference, clearance, and oil grooves/lubrication holes of the bearing.
  • Consider manufacturing limitations of the bearing material and whether standard products can be used.

v. Selecting the Primary Material

Select the primary material upon considering whether the corresponding design factors are within the allowed ranges.

vi. Checking the Test Data/Characteristics

Finally, check the test data and characteristics of the selected bearing. If required, conduct tests to check the performance. When using bearings in newly developed industrial machinery, it is important to select bearings with the required performance based on test data.

These are the six steps for selecting a plain bearing. Design Support Tools provided by Oiles Corporation can also be used to help select the optimal bearing in more detail. Utilize these tools when considering the type of plain bearing to use.

(2) How to Select a Rolling Bearing

This section describes how to select a rolling bearing.

i. Clarifying the Usage Conditions

First, it is necessary to clarify the conditions for using the bearing.

For example, check for details of the following.

  • What kind of loads will the bearing be subjected to?
  • How fast will the rotational speed be?
  • What conditions will the usage environment be subjected to?

ii. Selecting the Type and Layout of the Bearing

Next, select an appropriate bearing type and layout based on the usage conditions.

For example, when the bearing will only be subject to a radial load, it is suitable to use a deep groove ball bearing, which is the most common type of radial ball bearing. In cases where the bearing will also be subject to a thrust load, a combination of angular ball bearing and thrust bearing will be required, in order to simultaneously support the radial load and thrust load in one direction.

Multiple types of bearings can be combined in this manner to achieve optimal load dispersion and durability.

iii. Deciding the Bearing Dimensions

Decide the bearing dimensions based on the inner diameter (shaft diameter). The bearing dimensions must be decided in consideration of the allowed load, allowed rotation speed, and the space limitations of the machinery. The dimensions are directly related to the design efficiency and performance optimization of the machinery.

iv. Deciding the Bearing Precision

Decide the required precision. High-precision bearings minimize frictional resistance and vibration, and improve the life and efficiency of machinery. For precision machinery and machinery that rotates at high speed in particular, it is necessary to select a bearing with a high grade of precision as defined in JIS or ISO standards.

v. Deciding the Material and Lubrication Method

Finally, decide the material and lubrication method for the bearing according to the usage environment. For high-temperature environments, we recommend the use of a bearing made from highly heat-resistant material. For dusty environments or environments submerged in water, we recommend a shielded bearing or stainless steel bearing. The selection of an appropriate lubricant will also extend the bearing life and help maintain performance.

6. Conclusion

Bearings are mechanical components that support smooth operation by reducing the frictional resistance of machine parts that perform motion such as rotation. There are two types of bearings, which are plain bearings and rolling bearings. The type of bearing to use must be selected according to the required characteristics and intended use.
Plain bearings are suitable for situations requiring load-bearing capacity and impact resistance, as well as use in harsh environments. Rolling bearings are suitable for high-precision environments with high rotation speed.
We recommend selecting the suitable bearings for your needs upon clarifying the conditions under which they will be used.

Oiles Corporation is a leading manufacturer of oil-less bearings, boasting the world’s number one market share in bearings for a number of components.
To consult us on ways to use plain bearings or if you are considering incorporating plain bearings in your products, please contact us at Oiles Corporation. With our advanced technology and abundant know-how related to bearings, we can suggest a variety of options.

Oiles Corporation