As bearing operational conditions vary depending on devices in which bearings are mounted, different performances are demanded of bearings. Normally, two or more bearings are used on one shaft.
In many cases, in order to locate shaft positions in the axial direction, one bearing is mounted on the fixed side first, then the other bearing is mounted on the free side.
Table 4-1 Bearings on fixed and free sides
Recommended bearing type
Fixed side bearing
This bearing determines shaft axial position.
This bearing can accommodate both radial and axial loads.
Since axial load in both directions is imposed on this bearing, strength must be considered in selecting the bearing for this side.
Deep groove ball bearing Matched pair or stack angular contact ball bearing Double-row angular contact ball bearing Self-aligning ball bearing Cylindrical roller bearing with rib (NUP and NH types) Double-row tapered roller bearing Spherical roller bearing
Free side bearing
This bearing is employed to compensate for expansion or shrinkage caused by operating temperature change and to allow ajustment of bearing position.
Bearings which accommodate radial load only and whose inner and outer rings are separable are recommended as free side bearings.
In general, if non-separable bearings are used on free side, clearance fit is provided between outer ring and housing to compensate for shaft movement through bearings. In some cases, clearance fit between shaft and inner ring is utilized.
Separable types Cylindrical roller bearing (NU and N types) Needle roller bearing (NA type, etc.)
When bearing intervals are short and shaft shrinkage does not greatly affect bearing operation, a pair of angular contact ball bearings or tapered roller bearings is used in paired mounting to accommodate axial load.
After mounting, the axial clearance is adjusted using nuts or shims.