Mounting bearings with a cylindrical bore
With non-separable bearings, the ring that is to have the tighter fit is usually mounted first.
If the fit is not too tight, small bearings can be driven into position by applying light hammer blows to a sleeve placed against the bearing ring side face. The blows should be evenly distributed around the ring to prevent the bearing from tilting or skewing. The use of a bearing fitting tool (fig. 1) or a mounting dolly (fig. 2) instead of a sleeve enables the mounting force to be applied centrally.
Large numbers of bearings are generally mounted with a press.
If a bearing has to be pressed onto the shaft and into the housing bore at the same time, the mounting force must be applied equally to both rings and the abutment surfaces of the mounting tool must lie in the same plane. Whenever possible, mounting should be done with an SKF bearing fitting tool (fig. 1).
With self-aligning bearings, the use of an intermediate mounting ring prevents the outer ring from tilting and swiveling when the bearing and shaft assembly is introduced into the housing bore (fig. 3). The balls of larger self-aligning ball bearings in the 12 and 13 series protrude from the sides of the bearing. This design feature needs to be considered when mounting these bearings.
With separable bearings, the inner ring can be mounted independently of the outer ring, which simplifies mounting, particularly where both rings have an interference fit. When mounting the shaft and inner ring assembly into the housing containing the outer ring, careful alignment is required to avoid scoring the raceways and rolling elements. When mounting cylindrical or needle roller bearings with an inner ring without flanges or a flange on one side, a guiding sleeve should be used (fig. 4). The outside diameter of the sleeve should be the same as the raceway diameter of the inner ring and should be machined to tolerance class d10 for cylindrical roller bearings, and to tolerance 0/–0,025 mm for needle roller bearings.
It is generally not possible to mount larger bearings without heating either the bearing or the housing, as the force required to mount a bearing increases considerably with increasing bearing size.
The requisite difference in temperature between the bearing ring and shaft or housing depends on the degree of interference and the diameter of the bearing seat. Open bearings must not be heated to more than 120 °C (250 °F). SKF does not recommend heating bearings capped with seals or shields above 80 °C (175 °F). However, if higher temperatures are necessary, make sure that the temperature does not exceed the permissible temperature of either the seal or grease, whichever is lowest.
When heating bearings, local overheating must be avoided. To heat bearings evenly and reliably, SKF recommends using SKF electric induction heaters (fig. 5). If hotplates are used, the bearing must be turned over a number of times. The seals on sealed bearings should never contact the heating plate directly. Place a ring between the plate and bearing.