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

Before mounting, be sure you have all the necessary parts, tools, equipment and data available and ready to use. Review any drawings or instructions to determine the correct sequence and orientation in which components are to be assembled. Leave the bearings in their original packages until immediately before mounting so that they are not exposed to any contaminants. If there is a risk that the bearings have become contaminated because of improper handling or damaged packaging, they should be washed, dried and inspected before mounting.

Assembly area

Bearings should be mounted in a dry, dust-free area, away from machines producing swarf and dust. When bearings have to be mounted in an unprotected area, which is often the case with large bearings, steps should be taken to protect the bearing and mounting position from contaminants such as dust, dirt and moisture. This can be done by covering or wrapping bearings and machine components with plastic or foil.

Checking associated components

Housings, shafts, seals and other components of the bearing-shaft-housing system should be checked to make sure they are clean. This is particularly important for lubrication holes and threaded holes, lead-ins or grooves where remnants of previous machining operations might have collected. Also, make sure that all unpainted surfaces of cast housings are free of core sand and that any burrs are removed.

When all components have been cleaned and dried, check the dimensional and geometrical tolerances of each piece. The bearings only perform satisfactorily if the associated components comply with the prescribed tolerances. The diameters of cylindrical shaft and housing seats are usually checked with a micrometer, or internal gauge, at two cross-sections and in four directions (fig. 1). Tapered shaft seats can be checked using a ring gauge (GRA 30 series), a taper gauge (DMB or 9205 series) or a sine bar.

Removing the preservative

Normally, the preservative applied to new bearings does not need to be removed. It is only necessary to wipe off the outside and bore surfaces. However, if the lubricant to be used is not compatible with the preservative, the bearing should be washed and dried carefully. Bearings capped with seals or shields are filled with grease and should not be washed prior to mounting.

Bearing handling and safety

SKF recommends use of personal protection clothing and equipment, such as gloves, safety shoes and goggles, as well as carrying and lifting tools (fig. 2) that have been specially designed for handling bearings. Using the proper tools enhances safety, while saving time and effort.

When handling hot or oily bearings, SKF recommends wearing the appropriate heat or oil resistant gloves (fig. 3).

For large, heavy bearings, use lifting tackle that supports the bearing from the bottom (fig. 4). A spring between the hook and tackle can facilitate positioning of the bearing onto the shaft.

To ease lifting, large bearings can be provided, on request, with threaded holes in the ring side faces to accommodate eye bolts. These holes are designed to bear only the weight of the bearing, because the size and depth of the hole is limited by the ring thickness. Make sure that the eye bolts are only subjected to load in the direction of the shank axis (fig. 5).

Methods and tools

Depending on the bearing type and size, mechanical, thermal or hydraulic methods are used for mounting (→ SKF methods and tools [PDF]). Bearing sizes are categorized as follows:

  • small →  d ≤ 80 mm 
  • medium-size →  80 mm < d < 200 mm 
  • large →  d ≥ 200 mm
In all cases, it is important that the bearing rings, cages and rolling elements or seals are never struck directly with any hard object and that the mounting force is never applied through the rolling elements.

For an interference fit, the mating surfaces should be coated with a thin layer of light oil. For a loose fit, the mating surfaces should be coated with SKF anti-fretting agent.

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