The various bearing types and sizes require different mounting methods. Depending on the individual conditions these can be mechanical, hydraulic or thermal.
As the hardened bearing rings are sensitive to blows, these must never be applied directly to the rings. On mounting of non-separable bearings, the mounting forces must always be applied to the ring which will have the tight fit and therefore is the first to be mounted. Forces applied to the ring with the loose fit would be transmitted by the rolling elements, thus damaging raceways and rolling elements.
Mounting of separable bearings is easier, since the two rings can be mounted separately. In order to avoid score marks during assembly, slightly rotate the parts.
Mounting of Cylindrical Bore Bearings
Bearings with a maximum bore of approximately 80 mm can be mounted cold. The use of a mechanical or hydraulic press is recommended.
If no press is available, the bearing can be driven on the shaft by gentle taps with a hammer or mallet. However, a mounting sleeve of soft steel and with a flat face must be used in order to distribute the mounting force evenly over the entire ring circumference and to avoid damage to the bearing
The inside diameter of the sleeve should just be little larger than the bearing bore and, to avoid damage to the cage, its outside diameter should not exceed the inner ring shoulder height. If a self-aligning bearing has to be pressed on the shaft and pushed into the housing at the same time, a disk should be used which bears against both bearing rings, thus avoiding misalignment of the outer ring in the housing.
Mounting of Needle Roller Bearings
Needle Roller Bearings with Machined Rings The same mounting principles apply to needle roller bearings as to
cylindrical roller bearings. Bearings mounted in groups must have the same radial clearance to ensure uniform load distribution. Drawn Cup Needle Roller Bearings Due to their thin outer rings the form accuracy for the drawn cup needle roller bearings is achieved by means of tight fits in the housing, making a lateral location unnecessary.
For mounting drawn cup needle roller bearings, special mounting mandrels are used. Usually the mandrel abuts the stamped bearing face which is hardened with smaller sizes. If the mounting mandrel is accurately dimensioned, it can be applied to an unhardened lip without deforming or jamming the needle roller and cage assembly
Needle Roller and Cage Assemblies
Needle roller and cage assemblies are mounted between shaft and housing. In order to avoid score marks on the raceways and needle rollers, the needle roller and cage assemblies should be slightly turned and remain unloaded on mounting. Needle roller and cage assemblies can be axially guided in the housing or on the shaft.
The distance between the lateral cage guiding surfaces must be large enough (tolerance H11) to prevent the needle roller and cage assembly from jamming. The radial clearance of needle roller and cage assemblies depends
on the machining tolerances of the hardened and ground raceways on the shaft and in the housing. Needle roller and cage assemblies mounted in groups must be fitted with needle rollers of the same tolerance group.
Combined Needle Roller Bearings
The tight fits for the combined needle roller bearings require relatively high mounting forces. This must be borne in mind especially for needle roller-thrust ball bearings and needle roller-cylindrical roller thrust bearings with dust shield, where the ball or roller assembly of the thrust bearing is non-separable. It is advantageous to heat the
housings for pressing-in these bearings.
Mounting of Tapered Bore Bearings
Bearings with tapered bore are either fitted directly on the tapered shaft journal or, if the shaft is cylindrical, on an adapter sleeve or a withdrawal sleeve. The oil film applied to the washed out bearing bore, shaft and sleeve
should be very thin. A heavier coating would reduce friction and thus ease mounting; however, in operation the lubricant would be gradually forced out from the joint with a slackening effect on the tight fit, causing the ring or sleeve to creep and corrosion to develop on the surfaces. Forcing the bearing onto the tapered seat expands the inner ring and reduces radial clearance. Therefore the reduction in radial clearance can be used as a measure of the seating condition of the inner ring.
The reduction in radial clearance is the difference between the radial clearance prior to mounting and the radial clearance after bearing mounting. It is necessary to determine the initial radial clearance before mounting and then to check the clearance repeatedly during mounting until the proper amount of reduction and thus the required tight fit are obtained.
Instead of measuring the reduction in radial clearance the distance the bearing is forced onto the tapered seat can be measured. For the standard inner ring bore taper of 1:12 the ratio of axial drive-up to radial clearance reduction is approximately 15:1. This ratio considers the fact that the expansion of the inner ring is more than 75 to 80%
of the amount of interference existing between the fitted parts. If, with small bearings, the exact axial drive-up cannot be measured, the bearing should be mounted outside the housing. The bearing should be driven up the tapered seat just enough to still turn smoothly and to allow the outer ring to be easily swivelled by hand. The serviceman must have a “touch” for the smooth running feature.