A 16 3. Selection of bearing type In selecting bearings, the most important thing is to fully understand the operating conditions of the bearings. The main factors to be considered are listed in Table 3-1, while bearing types are listed in Table 3-2. Table 3-1 (1) Selection of bearing type Items to be considered Selection method Reference page No. 1) Installation space Bearing can be installed in target equipment *When a shaft is designed, its rigidity and strength are considered essential; therefore, the shaft diameter, i.e., bore diameter, is deter- mined at start. For rolling bearings, since wide variety with dif- ferent dimensions are available, the most suit- able bearing type should be selected. (Fig. 3-1) A 52 2) Load Load magnitude, type and direction which applied Load resistance of bearing is specified in terms of the basic load rating, and its value is specified in the bearing specification table. *Since various types of load are applied to bear- ings, load magnitude, types (radial or axial) and direction of application (both directions or single direction in the case of axial load), as well as vibration and impact must be considered in order to select the proper bearing. *The following is the general order for radial resistance ; deep groove ball bearings < angular contact ball bearings < cylindrical roller bearings < tapered roller bearings < spherical roller bearings A 18 (Table 3-2) A 87 3) Rotational speed Response to rotational speed of equipment in which bearings will be installed The limiting speed for bear- ing is expressed as allow- able speed, and this value is specified in the bearing specification table. *Since the allowable speed differs greatly depend-ing not only upon bearing type but on bearing size, cage, accuracy, load and lubrica- tion, all factors must be considered in selecting bearings. *In general, the following bearings are the most widely used for high speed operation. deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings A 18 (Table 3-2) A 84 4) Running accuracy Accurate rotation delivering required performance Dimension accuracy and running accuracy of bearings are provided by JIS, etc. *Performance required differs depending on equipment in which bearings are installed : for instance, machine tool spindles require high running accuracy, gas turbines require high speed rotation, and control equipment requires low friction. In such cases, bearings of tolerance class 5 or higher are required. *The following are the most widely used bear- ings. deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings A 18 (Table 3-2) A 58 5) Rigidity Rigidity that delivers the bear- ing performance required When load is applied to a bearing, elastic deformation occurs at the point where its rolling elements contact the raceway surface. The higher the rigidity that bearings possess, the better they control elastic deforma- tion. *In machine tool spindles and automobile final drives, bearing rigidity as well as rigidity of equipment itself must be enhanced. *Elastic deformation occurs less in roller bear- ings than in ball bearings. *Rigidity can be enhanced by providing preload. This method is suitable for use with angular con- tact ball bearings and tapered roller bearings. A 18 (Table 3-2) A 112