1. Clarify the Operating Conditions
This forms the foundation of bearing selection. You need to understand the load type—whether it primarily bears radial loads (e.g., motor shafts), axial loads (e.g., crane hooks), or combined loads—as well as the load magnitude (light, medium, or heavy), speed requirements (low, medium, or high), operating temperature range, and environmental conditions such as the presence of dust, moisture, or corrosive media.
2. Determine the Bearing Type
Select the appropriate bearing type based on operating conditions. Deep groove ball bearings work well for high-speed, light to medium pure radial loads due to their simple structure and low cost. Cylindrical roller bearings are ideal for high-speed, heavy radial loads, offering 30%-50% higher load capacity than deep groove ball bearings. Angular contact ball bearings can withstand both radial and axial loads, making them common in machine tool spindles, while tapered roller bearings suit large combined radial and axial loads like those in automobile wheel hubs. Self-aligning ball bearings accommodate angular deviations between shafts and housings, and thrust ball bearings are for axial loads only but not high speeds.
3. Choose the Bearing Precision Class
Select according to equipment requirements: Class P0 (normal class) for general machinery like agricultural equipment and conveyors; Class P6 for more precise machinery such as motors and water pumps; Class P5 for precision machine tools and printing machinery; and Class P4/P2 for high-precision equipment like CNC machine tools and aircraft engines.
4. Determine the Bearing Dimensions
Select appropriate bearing inner and outer diameters based on the shaft diameter and housing bore diameter. Consider installation space constraints and choose the smallest possible size while still meeting load capacity requirements.
5. Select Bearing Clearance
Radial clearance should be chosen based on operating temperature and interference fit, with larger clearance needed for higher temperatures or larger interferences. Axial clearance is mainly relevant for bearings subject to axial loads.
6. Consider Bearing Cage and Seal Type
For cages, brass is preferred for high-speed applications while steel works better for heavy loads. Regarding seals: open bearings suit applications requiring regular maintenance and lubrication; double rubber seals (2RS) work for environments with little dust and needing protection; and double metal shields (ZZ) are suitable for high-temperature environments.