What Is a Bearing?
A bearing is an essential tribological constituent and a standard fundamental part of several types of machinery. Generally, bearings are referred to as the joint of machinery and are available in different shapes and forms. They guide and support the rotational movement’s shaft and withstand the load transmitted from the shaft to the frame. They direct predefined motion in a system that may be under dynamic or static loading.
For instance, a sliding door only opens or functions because it permits sliding. It cannot be removed or lifted from its position. Thus, the only possible movement is limited to sliding motion by the installed bearing.
However, bearings are usually categorized based on the presence or absence of rolling bodies: rolling bearings and plain bearings. The rolling bearings include cylindrical roller bearings, ball bearings, and tapered roller bearings.
Meanwhile, thrust bearings and centripetal bearings are categorized based on their bearing characteristics. Radial ball bearings and radial roller bearings belong to the radial bearings category. Also, the thrust bearings category includes thrust roller bearings and thrust ball bearings.
How Does a Bearing Work?
A bearing reduces friction in machinery by means of a rolling motion. These supporting elements guide and constrain moving parts’ motion in all types of machinery. The Bearing acts as the stationary element that carries the dynamic and static load.
It supports the loads with the aid of components like balls or rollers that roll against the metal surfaces while in motion. The ball and roller bearings handle the load in this bearing assembly.
The rolling bearing reduces friction using its rolling motion, while the plain bearing uses sliding motion. These mechanisms ensure a greater reduction in energy consumption degrees during rotation.
Why Are Bearings Important?
Bearings play a vital role in the support mechanisms of the different machinery and industrial equipment types. The components prevent direct metal contact between two elements that are in relative motion.
These bearings reduce the wear and tear of parts by preventing friction and heat buildup. Besides, bearing reduces energy consumption in machinery by substituting sliding motion with low-friction rolling.
Moreover, bearings transfer the load of the rotating element to the housing. The rotating element’s load may be axial, radial, or combined loads. Likewise, a bearing can restrict the moving part’s freedom of movement in specific directions.
Types of Bearing
There are different types of bearing with varying purposes. This section discusses the commonly used bearings with their unique characteristics:
Plain Bearings
Plain bearings are the simplest types of bearing employed in industrial machinery. These bearings have a specific bearing surface with no rolling elements. It is a sleeve installed on the shaft, fitting into the hole or bore. These are often inexpensive, smooth, and efficient and make little-to-no noise when working. They are lightweight and have great load-carrying capacity.
Plain bearings are used for oscillatory, rotational, reciprocating, or sliding motion. The journal slides on the bearing’s inner surface while the bearing maintains a stationary position. However, combining machining materials with low coefficients of friction, like copper alloys, is advisable to allow smooth movement.
Besides, these bearings can accommodate some multi-directional movements and misalignment, which is ideal for static and dynamic loads. Typical applications of the plain bearings include marine, agriculture, construction, and automotive industries.
Fluid Bearings
Fluid bearings are advanced types of bearings that take over from metal bearings. These bearings use fluid exposed to the contact between two elements that mitigate friction. As a result, the two elements remain apart and don’t come close to each other due to the fluid pressure.
These bearings produce little noise during operation and less vibration than most metal bearings.
Angular Contact Ball Bearings
The inner and outer races of the angular contact ball bearings experience a shift towards each other along the bearing axis. These bearings can handle moderate axial loads in both paths and high radial loads.
You can move the axial load to the housing through the bearing due to the shift in the displacement in the inner race and outer race. Thus, this bearing is ideal for applications that require highly rigid axial guidance.
Engineers commonly use these bearings in high-speed applications like CNC machining tool spindles. Other typical applications include automobiles, agricultural equipment, gearboxes, and pumps.
Cylindrical Roller Bearings
This type of bearing is the simplest in the roller bearing category and can withstand the high demands of heavy radial loading and high speed. A cylindrical roller bearing delivers excellent stiffness, long service duration, low friction, and axial load transmission.
You can further increase the load capacity of this bearing type by removing the cages or retainers installed to hold the cylindrical rollers. Therefore, you can fit more rollers to carry the load properly. Cylindrical roller bearings are of various types: single-row, double-row, and four-row variants. Likewise, they are available in sealed and split variants.
These sealed variants are typical maintenance-free options because their bearing is prevented from contamination, and lubricant is preserved. Meanwhile, the split variants are commonly used for difficult-to-reach areas such as engine crankshafts.
Deep Groove Ball Bearings
The deep groove ball bearing comprises a ring of balls held in place by two races that transfers the load and permits rotational motion between the two races. A retainer holds the balls in position and is capable of absorbing radial forces.
Generally, they have very low rolling friction and are designed for low noise and vibration. Thus, these bearings are the most used ball-bearing variant, especially for high-speed applications.
This type of bearing installation is easy and needs little maintenance. However, you must install with caution to prevent situations like denting the races while they push fit onto shafts.
Needle Roller Bearings
These needle roller bearings have small radial sizes and very high load-carrying capacity. It offers free end support use but cannot support the axial load. It is adaptive to small and lightweight industrial machinery and equipment.
Needle roller bearings exhibit a high coefficient of friction and are perfect for higher speeds.
Thrust Roller Bearings
The thrust roller bearings can only bear unidirectional axial loads and minor shocks. They offer sizeable axial load capacity, large bearing rigidity, low sensitivity to shock load, and small space occupation.
They are ideal for low speed and are commonly used in work cases where thrust ball bearing are unsuitable. However, installing these bearings does not permit tilting the shaft’s axis and the rings.
Thrust Ball Bearings
These are unique bearings specially designed to support axial forces. Thrust ball bearings design offers minimal noise and seamless operation. More so, they are suitable for high-speed applications.
However, these bearings are available as single-direction or double-direction bearings, and their selection depends on whether the load is unidirectional or bidirectional.
Below are the primary working conditions that may require the use of a ball bearing:
- Ball bearings are ideal when thrust loads are present. The bearing’s design equips them with the ability to resist axial loads.
- Thrust ball bearings offer high speeds due to their small point of contact, resulting in minimal friction. Hence, there is minimal resistance for the bearings to overcome.
- The bearing centralizes all force onto limited contact points because of its ball-shaped rolling components. As such, early failure is unavoidable with high or heavy loads.
Tapered Roller Bearings
The tapered roller bearing features sections of a cone as a load-carrying component. These rollers stay between the two races in a hollow cone. The races and axes of the inner and outer ring rollers would intersect at a common point if extended.
Tapered rollers are generally grouped into single-row, double-row, and four-row and other types according to the installed number of rollers. These bearings are specifically built to support large thrust and large radial loads.
Thus, it determines the increase in axial bearing capacity. Tapered roller bearings are commonly installed in pairs, facing opposite directions for better thrust handling in both directions. Typical applications of tapered roller bearings include car hubs.
Magnetic Bearings
These bearings use the idea of magnetic elevation to station the shaft mid-air. Magnetic bearings ensure zero-wear bearings due to their no physical contact characteristics. These bearings are categorized into two major types, namely active and passive magnetic bearings. More importantly, the maximum relative speed it can handle has no limits.
Magnetic bearings are immune to certain irregularities in shaft design as the shaft adjusts its position automatically depending on its center of mass. However, it may counteract one side but will eventually function effectively.
Self-Aligning Ball Bearings
Self-aligning ball bearings are not susceptible to misalignment between the housing and the shaft, which results from mounting errors or shaft deflection. These bearings possess an inner ring with deep groves similar to deep groove ball bearings accompanied by two rows of balls and the external ring.
The outer ring’s concave shape allows the inner ring to rearrange or realign itself based on the misalignment.
Common Application of Bearings
Bearings have common uses in different machinery and industries where they facilitate smooth motion, mitigate friction, and support loads. Below are typical applications of bearings:
Industry Machinery
Bearings are vital in various industrial equipment and machinery, including turbines, pumps, gearboxes, compressors, robotics, and conveyors. They support the loads involved in this application and are responsible for the smooth rotation of shafts.
Medical Equipment
Manufacturers incorporate bearings in medical devices and equipment like dental equipment, CT scanners, X-ray scanners, and surgical tools for low-friction performance and precise motion.
Automotive Industry
The automotive industry uses various bearings in engineering components, such as engine bearings, transmission bearings, wheel bearings, steering system bearings, and differential bearings.
Railway Industry
Railway applications for bearings include wagons, locomotives, and rolling stock components to support wheels, axles, and rotary components.
Aerospace Industry
The aerospace sector utilizes bearings subjected to strict requirements for reliability and performance. Bearings are often used in landing gear systems, aircraft engines, control systems, and several other military and commercial aircraft applications.
Marine Industry
Marine engineers use bearings in marine applications for cranes, steering systems, propulsion systems, winches, and various equipment with high load support and smooth rotation requirements in challenging marine conditions.
Engineering Tips on Determining the Ideal Bearing for Your Project
This section discusses different tips on how to choose between the different types of bearing:
Rotation Speed
Rotational or linear speed requirements are essential to determine the ideal bearing. These bearings often have certain speed levels that show their maximum permissible operating speed. Using deep groove ball bearings, cylindrical roller bearings, or angular contact bearings in higher-speed working conditions is advisable. Conversely, tapered roller bearings are ideal for use in lower-speed working conditions.
Furthermore, the thrust ball bearings provide a lower speed limit, making it suitable for lower-speed conditions—nevertheless, the smaller the size of the same type of bearings, the higher their allowable speed. Therefore, ensuring the actual speed is lower than the limit speed when choosing bearings for your project is essential.
Rigidity
Bearing rigidity is a critical factor in machinery like machine tool spindles. Rolling bearings such as cylindrical and tapered roller bearings exhibit low elastic deformation as they are under load. The rigidity is poor as the raceway and the rolling body come in contact.
However, you can prevent shaft vibration and enhance the support’s rigidity by preloading specific axial force in different bearings like tapered roller and angular contact ball bearings. It ensures the compression is mutual.
Accuracy
Precision machining, instrumentation, and machine tool spindle require higher precision and tolerance. Besides, cylindrical roller bearings, angular contact balls, and deep groove balls are suitable for high rotational accuracy requirements.
More so, cylindrical roller bearings, deep groove ball bearings, and angular contact ball bearing require high rotational accuracy. However, using precision bearings with tighter tolerances helps meet the preferred specification for most machinery.
Load
It is essential to decide the type and size of the radial or axial loads that the bearing will handle. However, examine the bearing’s static and dynamic load capacities to ensure it can manage the expected loads without untimely failure.
Choose radial bearing when carrying the radial load in the direction vertical to the shaft. On the other hand, the axial bearing is suitable for bearing axial or thrust load when in the same direction as the shaft. Use a ball bearing when the bearing supports a small load, and use a roller bearing for a larger load.
Conclusion
Bearings are essential components that guide the predefined motion of industrial machines. These elements support the machinery’s rotary shaft, reducing friction between mobile parts. However, it is critical to understand the differences in the characteristics of these bearing types and consider various factors.
AT-Machining is the right partner for you whenever you need the help of professionals with choosing bearings for your parts. We offer you all the necessary manufacturing assistance, such as choosing suitable bearings and fasteners for your project. Contact us today, and let’s discuss your project!
