Mounting bearings with a cylindrical bore

Performance and operating conditionsBearing type and arrangementBearing sizeLubricationOperating temperature and speedBearing interfacesBearing executionSealing, mounting and dismounting

Non-separable bearings

With non-separable bearings, the ring that requires the tighter fit is usually mounted first.

Separable 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 with a flange on one side only, a guiding sleeve should be used (fig. 1). 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.

Cold mounting

If the fit is not too tight, small bearings can be driven into position by applying light hammer blows to a bearing fitting tool (fig. 2). The tool enables the mounting force to be applied centrally.
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. 2).
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. 4). The balls of larger self-aligning ball bearings in the 12 and 13 series protrude from the sides of the bearing, therefore the mounting ring must have a recess.

Hot mounting

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. Generally, 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. Read and follow the safety precautions below.
For additional information about these mounting methods, refer to the SKF bearing maintenance handbook.


Safety precautions for fluoro rubber and Polytetrafluoroethylene

Fluoro rubber (FKM) and Polytetrafluoroethylene (PTFE) are very stable and harmless up to normal operating temperatures of 200 °C (390 °F). However, if exposed to temperatures above 300 °C (570 °F), such as fire or the open flame of a cutting torch, FKM and PTFE give off hazardous fumes. These fumes can be harmful if inhaled, as well as if they contact the eyes. In addition, once the seals have been heated to such temperatures, they are dangerous to handle even after they have cooled. Therefore, they should never come in contact with the skin.

If it is necessary to handle bearings with seals that have been subjected to high temperatures, such as when dismounting the bearing, the following safety precautions should be observed:
  • Always wear protective goggles, gloves and appropriate breathing apparatus.
  • Place all of the remains of the seals in an airtight plastic container marked with a symbol for “material will etch”.
  • Follow the safety precautions in the appropriate safety data sheet (SDS).

If there is contact with the seals, wash hands with soap and plenty of water and, if contact has been made with the eyes, flush eyes with plenty of water and consult a doctor immediately. If the fumes have been inhaled, consult a doctor immediately.

The user is responsible for the correct use of the product during its service life and its proper disposal. SKF takes no responsibility for the improper handling of FKM or PTFE, or for any injury resulting from their use.
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