Rolling Bearing: 2024 Ultimate Guide

Dec 27, 2023

Since bearings are components that can play a fixed role in mechanical transmission and reduce the load friction coefficient, they play an irreplaceable role in today's mechanical equipment. They reduce the mechanical load friction coefficient of the transmission by supporting the mechanical rotating body. Bearings include two methods: rolling and sliding. Next, I will give you a little knowledge about rolling bearings!


Rolling Bearings Definition


A rolling bearing is a precision mechanical component that reduces friction loss by converting sliding friction between the shaft and the shaft seat into rolling friction. Ball bearings include four parts: inner ring, outer ring, rolling elements and cage. The inner ring rotates with the shaft, and the outer ring supports the bearing seat. The rolling elements are evenly distributed between the inner and outer rings and perform well. Life depends on the shape, size, and quantity; the cage can fix the position of the rolling elements, make the rolling elements rotate, and provide lubrication.


Characteristics of Rolling Bearings


1. Professionalism


The professionalism of rolling bearings is reflected in two aspects: bearing processing and production. Bearing processing requires a lot of special equipment, such as inkjets, grinding machines, etc.; bearing production requires steel ball and micro bearing production plants.


2. Technology


To produce bearings in batches and on a large scale, you must use advanced machine tools, molds and processes. CNC machine tools, three-jaw chucks, protective atmosphere heat treatment, etc., are required in the production process.


3. Automation


The professionalism of bearing production provides the foundation for the automation of bearing production. Extensively use automatic, semi-automatic special and non-special machine tools, gradually promoting automatic production lines. For example, heat treatment automatic lines, assembly automatic lines, etc.


Structural Composition of Rolling Bearings


The structure of a rolling bearing includes raceways, rolling elements and cages. The raceways include inner rings and outer rings. The rolling elements refer to rolling balls or rollers. The rollers are fixed in place under the action of the cage and keep moving.


1. The inner and outer ring raceways or raceway surfaces.


The raceway is the surface in contact with the rollers and is also called the raceway surface. The raceway surface plays the role of carrying the entire load of the bearing. Normally, the outer ring of the raceway is fixed on the bearing box, and the inner ring is fixed on the shaft.


2. Rolling elements


According to the shape of rolling elements, they can be divided into rolling balls and rollers. The shapes of rollers include cylindrical, needle-shaped, conical and drum-shaped spherical surfaces.

Theoretically and geometrically, the relationship between rolling elements and raceways can be seen as the contact between points and lines. The "point" of the rolling elements rolls and rotates on the "line" of the inner and outer raceways.


3. Cage


Cages include press-in, machined, and formed forms, which are divided according to the cage's production method. What bears the load in the bearing is the contact surface between the rolling elements and the raceway. The cage is only used to fix the position of the rolling elements so that They work in correct and appropriate positions and intervals and do not bear loads. The cage also ensures the bearing installation's safety and that the rolling elements will not fall off.


Division of Rolling Bearings


1. Construction


According to the structure of rolling elements and raceways:

Deep groove ball bearings, needle roller bearings, angular contact bearings, spherical roller bearings, thrust ball bearings, thrust spherical roller bearings, cylindrical roller bearings, tapered roller bearings, seated spherical ball bearings, etc.


According to the structure, rolling bearings can be divided into:


1) Deep groove ball bearings


Due to its simple structure and convenient application, deep groove ball bearings have become a type of bearing that is mass-produced and widely used. It can bear both radial load and large axial load. Based on these characteristics, deep groove ball bearings are mainly used in automobiles, tractors, machine tools, motors, pumps, agricultural machinery, textile machinery, etc.


Deep groove ball bearings

        Deep groove ball bearing      


2) Needle roller bearings


Needle roller bearings usually have thin and long rollers. The diameter of these rollers is less than five millimeters, and their length is three to ten times its diameter. Because of this characteristic, the radial arrangement of the needle rollers is dense, making the outer diameter Very small while maintaining the same inner diameter size and load-bearing capacity as other bearings; it is very suitable for support structures in installation scenarios with radial size requirements. You can choose bearings without inner rings, needle rollers and cages for different application scenarios as needed. In this way, the bearing's peripheral mirror surface and outer shell surface assume the role of the inner and outer surfaces of the raceway. In this way, to achieve production, Application requirements require higher accuracy and hardness of needle roller bearings, and the quality of the shaft and shaft housing is similar to that of bearings with ferrules. Because needle roller bearings only carry radial loads, they are often used in universal joint shafts, hydraulic pumps, sheet rolling mills, rock drills, gearboxes, automobile and tractor transmissions, etc.


Needle roller bearings

        Needle roller bearing      


3) Angular contact bearings


Due to its relatively high limit speed, angular ball bearings can bear both radial and axial loads and pure axial loads, and the contact angle determines the axial load. The greater the contact angle, the greater the axial load. big. Angular contact bearings are suitable for use in oil pumps, air compressors, various transmission devices, fuel injection pumps, printing machinery and other fields.


Angular contact bearings

          Angular contact bearing           


4) Aligning ball bearings


The self-aligning ball bearing contains two rows of steel balls. The inner ring comprises double raceways, and the outer ring raceway is shaped like an inner spherical surface. The characteristic is that it can be adjusted through the angular deviation of the axis line of the inner and outer raceways. For bearings, the shaft deflection and shell deformation will cause deviation. The self-aligning ball bearing can compensate for this deviation and is very suitable for use in parts where the bearing hole cannot guarantee complete coaxiality. This type of bearing can carry small axial and radial loads. The core application scenarios of self-aligning ball bearings are agricultural machinery, such as combine harvesters. They are also used in blowers, paper machines, textile machinery, woodworking machinery, bridge crane wheels and transmission shafts.


5) Spherical roller bearings


The characteristic of the self-aligning hybrid bearing is that it has a self-aligning function, which can compensate for the bearing error. Its principle is based on the two-part stick of spherical roller bearings, which can carry radial and axial loads in all directions. It has a strong load-bearing capacity and can work under heavy and vibration loads. Mainly used in papermaking machinery, reduction devices, gearboxes, various industrial reducers, railway vehicle axles, etc.


Spherical roller bearings

       Spherical roller bearing      


6) Thrust ball bearing


Thrust ball bearings are separable bearings in which the shaft ring and cage are separated. The shaft ring is a ferrule that fits with the shaft. The ferrule fits with the bearing seat hole and has a gap with the shaft. Reasoning ball bearings are smart oranges and cannot bear radial loads. One-way thrust ball bearings only carry one-way axial loads. Two-way thrust ball bearings can carry two-way axial loads. They are mainly used in the steering mechanism of automobiles. And machine tool spindles.


7) Thrust roller bearings


Thrust roller bearings can carry axial and radial loads, but they mainly carry axial loads, and the maximum radial load is fifty-five percent of the axial load. The advantages of reasoning roller loads are lower membrane material quotation and higher rotational speed while being able to align. Asymmetric spherical roller bearings can also effectively reduce the relative sliding of rollers and raceways during operation and can bear larger loads. They can be given priority during the selection and design process. They are mainly used in hydroelectric generators, Crane hooks, etc.


8) Cylindrical roller bearings


Cylindrical roller bearings usually only carry radial loads, and the bearing rings play a role in limiting and guiding, making the rollers, rings and cages a combined key and separated from other bearing rings. Cylindrical roller bearings are easy to install and disassemble. They are suitable for use in large motors, machine tool spindles, diesel engine crankshafts, axles, automobiles, and transmission boxes of supporting machines, etc.


 Cylindrical roller bearings

      Cylindrical roller bearing      


9) Tapered roller bearings


Tapered roller bearings are similar to thrust roller bearings and carry a combined axial and radial load, with the radial load being the main load. In addition, large tapered roller bearings mainly carry radial loads. This kind of bearing is detachable and can be installed independently on the inner or outer ring of the bearing. The radial clearance of the bearing can be adjusted, and the axial clearance can also be adjusted. It can be used in automobile rear axle hubs, large machine tool spindles, high-power reducers, axle bearing boxes or rollers of conveying devices.


10) Insert spherical ball bearing with seat


The seated outer ball bearing comprises a sealed outer spherical ball bearing and a steel plate stamped casting. The structure of outer ball bearings and deep groove ball bearings is the same, but the inner ring is wider than the outer ring. The outer ring is matched with the concave spherical surface of the bearing seat to achieve automatic alignment. There is generally a gap between the inner hole of this kind of bearing and the shaft, and the inner ring of the bearing needs to be fixed on the shaft so that it rotates with the shaft. The features of seated spherical ball bearings are compact structure, complete sealing, and convenient assembly. They are very suitable for use in simple supports. Commonly used scenarios are mining, metallurgy, textiles, printing and dyeing, agriculture, conveying machinery, etc.


2. Divide according to outer diameter size


Nominal Diameter of Bearings Name
Less than 26mm Miniature Bearings
28-55mm Small Bearings
60-115mm Small to Medium Bearings
120-190mm Large Medium Bearings
200-430mm Large Bearings
440-2000mm Extra Large Bearings
Greater than 2000mm Heavy-Duty Bearings


Comparison of advantages and disadvantages


Advantages Disadvantages
1. Reduces friction resistance, minimizes losses, improves efficiency, quick startup.      1. Complex bearing seat structure.
2. Standard size, interchangeable, easy maintenance and disassembly, compact size, long lifespan.      2. Higher cost.
3. High precision, capable of handling large loads.      3. Fatigue on rolling contact surfaces can lead to lubrication, dust and moisture protection, and normal operation failures. Consideration of self-aligning bearings is possible in various applications.
4. Can be mass-produced, high production efficiency, stable production quality, reduced production costs.  
5. Low friction heating and low wear during use, low sensitivity of bearings to deformation.  
6. Capable of simultaneously bearing radial and axial loads.  
7. Can withstand certain fluctuations while handling large loads and maintaining performance.


Maintenance of Rolling Bearings


1. Regulations on installation surface and installation location


Ensure that the installation environment and surface are clean and tidy. The entry of dust and iron filings will cause noise and abnormal movement when the bearing is working, causing damage to the raceways and rolling elements.


2. Cleaning specifications for bearings before installation


Except for fully enclosed bearings, others must be coated with anti-rust oil on the surface, scrubbed with clean oil, and installed and used under high-speed and high-temperature lubricating oil. The quality and vibration noise of bearings are greatly affected by cleanliness.


3. Precautions for lubrication


The main characteristics of lubricating oil are based on base oil. Low-viscosity base oil is used in low-temperature and high-speed situations, and high-viscosity grease is used in high-temperature and high-load situations. Viscosity also affects lubrication performance. Water resistance is based on the water resistance of the thickener. At the same time, care should be taken not to mix different brands of lubricants.


4. Amount of bearing lubricant


More lubrication is not better. Excess lubricating oil will cause excessive agitation of the grease inside the bearing, causing the temperature to be too high. The lubricant filled should not exceed one-half the internal size of the bearing, and the amount should be appropriately reduced at high speeds.


5. Precautions for installation and disassembly


During the installation process, the bearing's end face and non-stressed surface must not be directly hammered. Press blocks, sleeves, or other installation tools should be used to stress the bearing evenly. Installation will be smoother if lubricated on the mounting surface. If the fit interference is large, the bearing should be heated to 80 to 90°C in mineral oil and installed quickly. The oil temperature should not exceed 100°C to prevent the tempering effect from causing a decrease in hardness and affecting dimensional recovery. When disassembly is difficult, it is recommended that you use a disassembly tool to pull outwards while carefully pouring hot oil into the inner ring. The heat will expand the inner ring of the bearing and make it easy to fall off.


6. Control method of bearing radial clearance


The bearing radial clearance should be appropriately selected according to the specific conditions. The basic radial clearance group can be used under normal temperatures; large radial clearance can be selected under special conditions, such as high temperature, high speed, etc.; and smaller radial clearance is mainly used for precision and machine tool spindles. In addition, separable bearings do not require any clearance. It should be noted that the working clearance of the installed bearing is smaller than the clearance before installation to withstand the rotational load and elastic deformation.