Bearings are crucial components in mechanical equipment. Their primary function is to support rotating parts of machinery, reducing the coefficient of friction and mechanical load during transmission.
Bearings can be classified based on their load direction or nominal contact angle into:
Radial bearings
Thrust bearings
Based on the type of rolling element, bearings are classified into:
Ball bearings
Roller bearings
Based on whether they can self-align, bearings are categorized as:
Self-aligning bearings
Non-self-aligning bearings (rigid bearings)
Based on the number of rolling elements, bearings are classified into:
Single-row bearings
Double-row bearings
Multi-row bearings
Based on whether the components are separable, bearings are divided into:
Separatable bearings
Non-separable bearings
Additionally, bearings are also classified based on structural shape and size.
Angular Contact Ball Bearings The raceways and balls have a contact angle, with standard contact angles being 15°, 30°, and 40°. A larger contact angle increases axial load capacity, while a smaller contact angle is better for high-speed rotation. Single-row bearings can handle radial loads and single-direction axial loads. Structurally, two single-row angular contact ball bearings are combined back-to-back sharing inner and outer rings, which can handle radial loads and bidirectional axial loads.
Applications:
Single-row: Machine tool spindles, high-frequency motors, gas turbines, centrifugal separators, front wheels of small cars, and small gear shafts of differentials.
Double-row: Oil pumps, Roots blowers, air compressors, various types of gearboxes, fuel injection pumps, printing machinery.
Self-aligning Ball Bearings These bearings feature two rows of balls and an outer raceway with an inner spherical shape, allowing automatic adjustment for misalignment caused by shaft or housing deflection. They mainly bear radial loads and can be easily installed on shafts using fasteners.
Applications:
Woodworking machinery, textile machinery drive shafts, vertical self-aligning bearing units.
Self-aligning Roller Bearings These bearings contain spherical rollers between a spherical outer raceway and double raceways on the inner ring. They are divided into R, RH, RHA, and SR types based on internal structure. Due to the spherical shape of the outer raceway, these bearings can automatically adjust for misalignment caused by shaft or housing deflection. They can bear radial loads and bidirectional axial loads.
Applications:
Papermaking machinery, reduction gears, railway vehicle axles, rolling mill gearboxes, rolling mill roller ways, crushers, vibrating screens, printing machinery, woodworking machinery, various industrial reduction gears, and vertical self-aligning bearing units.
Thrust Self-aligning Roller Bearings These bearings have rollers arranged in an inclined manner, and the raceway surfaces are spherical, which allows for alignment adjustment. They can bear very large axial loads while also accommodating some radial loads. They generally use oil lubrication.
Applications:
Hydraulic generators, vertical electric motors, ship propeller shafts, reduction gears for rolling mills, tower cranes, coal mills, extruders, and forming machines.
Tapered Roller Bearings These bearings have tapered rollers guided by a large flange on the inner ring. The design ensures that the apex of the tapered surfaces of the inner and outer raceways and rollers intersect at the bearing centerline. Single-row bearings can handle radial loads and unidirectional axial loads, while double-row bearings can handle radial loads and bidirectional axial loads. They are suitable for heavy and impact loads.
Applications:
Automotive: Front and rear wheels, gearboxes, differential small gear shafts. Machine tool spindles, construction machinery, large agricultural machinery, railway vehicle gear reducers, rolling mill necks, and reduction gearboxes.
Deep Groove Ball Bearings These bearings have raceways on each ring with a cross-section approximately one-third of the circumference of the ball's equator. Deep groove ball bearings are primarily used to handle radial loads but can also accommodate some axial loads.
When the radial clearance of the bearing increases, it has the characteristics of angular contact ball bearings and can handle axial loads in both directions. Compared to other types of bearings with the same size, deep groove ball bearings have a lower friction coefficient, higher maximum speed, and precision, making them a preferred choice for users.
Applications:
Automotive, tractors, machine tools, motors, water pumps, agricultural machinery, textile machinery, etc.
Bearings consist of rings with raceways, balls, and cage assemblies. The raceway ring that fits with the shaft is called the inner ring, and the one that fits with the housing is called the outer ring. Bidirectional bearings have a central ring for secret shaft fitting, while unidirectional bearings can handle single-direction axial loads. Bidirectional bearings can handle bidirectional axial loads but cannot handle radial loads.
Applications:
Automotive steering pins, machine tool spindles.
Thrust Ball Bearings Thrust roller bearings are designed primarily to support axial loads and combined axial and radial loads, although the radial load should not exceed 55% of the axial load. Compared to other types of thrust roller bearings, this type has a lower friction coefficient, higher speed capabilities, and self-aligning abilities. The 29000 series bearings feature asymmetrical spherical rollers, which reduce relative sliding between the rollers and raceways during operation. These bearings have long, large-diameter rollers with a high number of rollers, resulting in a high load capacity. They typically use oil lubrication, though grease lubrication may be used in some low-speed applications.
Applications:
Hydraulic generators
Crane hooks
Cylindrical Roller Bearings Cylindrical roller bearings are guided by two flanges on one of the bearing rings. The bearing assembly consists of the rollers, cage, and the guiding ring, and is separable from the other bearing ring, making it a separable bearing.
These bearings are easy to install and disassemble, especially when the inner and outer rings are interference-fitted with the shaft and housing. They are generally used to support radial loads, although single-row bearings with flanges on both rings can handle small constant axial loads or larger intermittent axial loads.
Applications:
Large motors
Machine tool spindles
Wheel axle boxes
Diesel engine crankshafts
Automotive gearboxes
Four-Point Contact Ball Bearings These bearings can handle radial loads and bidirectional axial loads. A single bearing can replace the front or back combination of angular contact ball bearings and is suitable for pure axial loads or combined loads with a significant axial component. The bearing forms a contact angle in any direction of axial load, resulting in two-point contact on each side of the contact line.
Applications:
Jet engines
Gas turbines
Thrust Cylindrical Roller Bearings These bearings consist of a washer-shaped raceway ring (inner and outer rings) and cylindrical rollers with cages. The rollers are convexly ground to ensure uniform pressure distribution between the rollers and raceway, allowing them to support unidirectional axial loads with high axial stiffness.
Applications:
Oil drilling rigs
Iron and steel machinery
Thrust Needle Bearings Separable thrust needle bearings are composed of raceway rings, needles, and cage assemblies and can be combined with either stamped thin raceway rings or machined thick raceway rings. Non-separable thrust needle bearings are precision-stamped raceway rings with needles and cage assemblies, forming an integral bearing. These bearings handle unidirectional axial loads and are compact, facilitating space-efficient mechanical designs. They mostly use needle rollers and cages with the shaft and housing surfaces serving as the raceway.
Applications:
Automotive transmissions
Ploughing machines
Machine tools
Thrust Tapered Roller Bearings These bearings feature tapered rollers with a large end as a spherical surface. The rollers are accurately guided by the flanges of the raceway rings (inner and outer rings). The design ensures that the apex of the tapered surfaces of the inner and outer raceways and the rolling surfaces of the rollers intersect at the bearing centerline. Unidirectional bearings can handle unidirectional axial loads, while bidirectional bearings can handle bidirectional axial loads.
Applications:
Unidirectional: Crane hooks, oil drilling rig turntables
Bidirectional: Rolling mill roller necks
Pillow Block Spherical Ball Bearings Pillow block spherical ball bearings consist of two-sealed outer spherical ball bearings and a cast (or stamped steel) bearing housing. The internal structure of the outer spherical ball bearing is similar to that of deep groove ball bearings, but the inner ring is wider than the outer ring, and the outer ring has a spherical surface that aligns automatically with the concave surface of the bearing housing.
Applications:
Mining
Metallurgy
Agriculture
Chemical industry
Textile
Printing
Conveying machinery
