Mounting bearings with tapered bore
The inner rings of bearings with a tapered bore are always mounted with an interference fit. The degree of interference in this case is not determined by the chosen shaft tolerance, as with bearings having a cylindrical bore, but by how far the bearing is driven up onto the tapered seating. The original radial internal clearance is reduced in the process and this reduction gives an indication on the interference fit obtained.

For larger bearings, considerably more force is required to drive them up a tapered seating. The practical solution is to use an SKF hydraulic nut, which uses hydraulic power to provide the drive-up force. If the oil injection method is also employed, then the force required can be further reduced. The hydraulic nut is screwed onto a threaded section of the journal or sleeve thread, so that its annular piston abuts the inner ring of the bearing, a nut on the shaft, or a disc attached to the end of the shaft.

With the oil injection method, high-pressure oil is injected between the mating surfaces. The oil film formed separates the mating surfaces and appreciably reduces the friction between them. The method is mainly used when mounting bearings directly on tapered journals, but is also used to mount bearings on adapter and withdrawal sleeves, which have been prepared for the oil injection method. A pump or oil injector produces the required pressure, the oil being supplied to the mating surfaces via ducts and distribution grooves in the shaft or sleeve. The necessary ducts and grooves in the shaft must be considered when designing the bearing arrangement.

Degree of interference
A certain degree of interference is needed when mounting bearings with a tapered bore. Different methods can be applied to measure the degree of interference fit.

Measurement of clearance reduction with feeler gauges
For small and medium size bearings the reduction in radial internal clearance can be measured. Before mounting the bearing, the radial internal clearance is measured. During drive-up the reduction in radial internal clearance is checked, until the requisite value is obtained. To measure the clearance feeler gauges having blades with a thickness of 0,03 mm and above should be used.