Common rolling bearings
Rolling bearings are essential components in mechanical transmission systems. They achieve relative motion between the shaft and the bearing housing through the rolling of their rolling elements. They feature low friction, low power loss, and high precision, making them widely used in various mechanical equipment, including machine tools, automobiles, and motors. Commonly used rolling bearings are categorized by structural type into deep groove ball bearings, cylindrical roller bearings, tapered roller bearings, and thrust bearings. Each bearing type has its own unique structural design and load-bearing characteristics, meeting the requirements of various operating conditions. For example, deep groove ball bearings can withstand both radial and axial loads, while cylindrical roller bearings offer a high radial load capacity, providing diverse solutions for the stable operation of mechanical systems.
Deep groove ball bearings are the most widely used type of rolling bearing. Their structural features include deep groove raceways on both the inner and outer rings, steel balls as rolling elements, and self-aligning, eliminating the need for strict alignment. The radial clearance of these bearings can be adjusted according to application requirements and is classified into five grades: C2, C0, C3, C4, and C5. Grade C2 has the smallest clearance and is suitable for high-precision machine tool spindles; grades C3 and C4 have larger clearances and are suitable for high-temperature environments or high-speed rotation. Deep groove ball bearings have a nominal contact angle of 0° and primarily support radial loads, but can also withstand certain axial loads. They are widely used in equipment such as motor rotors, automotive transmissions, and water pumps. The 6200 series deep groove ball bearing is the most common model, with an inner diameter ranging from 10mm to 100mm. Its maximum speed can reach over 15,000 rpm and can be lubricated with grease or oil for long-term stable operation.
Cylindrical roller bearings are renowned for their exceptional radial load capacity. Their cylindrical rolling elements form linear contact with the raceways, enabling them to withstand significant radial forces and shock loads. These bearings are categorized by structure as single-row, double-row, and multi-row cylindrical roller bearings. Single-row cylindrical roller bearings (such as the N series) offer a simple structure and are suitable for carrying purely radial loads. Double-row cylindrical roller bearings (such as the NN series) offer greater rigidity and are commonly used in applications requiring high rigidity, such as machine tool spindles. The inner and outer rings of cylindrical roller bearings can be separated for easy installation and disassembly, and radial clearance can be precisely controlled by adjusting the relative position of the inner and outer rings. In large-scale machinery, such as rolling mill work rolls and crane drums, multi-row cylindrical roller bearings can further increase load capacity by increasing the number of rolling elements, ensuring reliable operation under heavy loads.
The raceways and rolling elements of tapered roller bearings are conical, with a nominal contact angle between 10° and 30°. They can simultaneously withstand large radial and axial loads, and their load-bearing capacity increases with increasing contact angle. These bearings are typically used in pairs. During installation, the clearance can be controlled by adjusting the axial position of the inner and outer rings to achieve a preload effect, improving the rigidity and rotational accuracy of the shafting. The 30200 series tapered roller bearings are a commonly used model, widely used in transmission components such as automotive rear axles, reducers, and machine tool spindle boxes. Their outer rings and bearing seats use a transition fit, while the inner rings and shafts use an interference fit to ensure no relative slip when transmitting torque. The disadvantage of tapered roller bearings is their poor high-speed performance, with a maximum speed typically lower than that of deep groove ball bearings. Therefore, they are more suitable for medium- and low-speed, heavy-load operating environments.
Thrust bearings are specifically designed to carry axial loads. Based on the type of rolling elements, they can be categorized as thrust ball bearings and thrust roller bearings. Their structural characteristics are characterized by a large axial load-bearing area. Thrust ball bearings (such as the 51100 series) use steel balls as rolling elements and are suitable for applications with low axial loads and high speeds, such as axial positioning of machine tool spindles. Thrust roller bearings (such as the 81100 series) use cylindrical or tapered rollers as rolling elements and can withstand greater axial loads. They are widely used in heavy equipment such as turbines and cranes. Thrust bearings have strict installation requirements, requiring alignment of the shaft and housing axes to avoid premature failure due to misalignment. Furthermore, combination bearings (such as angular contact ball bearings and cylindrical roller bearings) combine the advantages of multiple bearing types and are used in high-precision, high-speed precision machine tool spindles. Through appropriate configuration, they optimize the distribution of radial and axial loads, meeting the stringent bearing performance requirements of modern machining.
