In many cases, one of the principal dimensions of a bearing - the bore diameter - is predetermined by the machine's design and the shaft diameter.
For small-diameter shafts all types of ball bearings can be used, the most popular being deep groove ball bearings; needle roller bearings are also suitable (fig 1). For large-diameter shafts, cylindrical, tapered, spherical and toroidal roller bearings are available, as well as deep groove ball bearings (fig 2).
When radial space is limited, bearings with a small cross section, particularly those with a low cross-sectional height, should be chosen, i.e. bearings in the 8 or 9 Diameter Series (see under Dimensions in the "Bearing data - general" section). Needle roller and cage assemblies, drawn cup needle roller bearings and needle roller bearings without or even with an inner ring (fig 3), are very appropriate as well as certain series of deep groove and angular contact ball bearings, cylindrical, tapered, spherical and toroidal roller bearings.
When axial space is limited, certain series of cylindrical roller bearings and deep groove ball bearings can be used for radial or combined loads respectively (fig 4) as well as the various types of combined needle roller bearings (fig 5). For purely axial loads, needle roller and cage thrust assemblies (with or without washers) as well as thrust ball bearings and cylindrical roller thrust bearings can be used (fig 6).