Self-Aligning Ball Bearings

Mounting bearings with a tapered bore

Self-aligning ball bearings with a tapered bore are always mounted with an interference fit on a tapered shaft seat or an adapter or withdrawal sleeve. As a measure of the degree of interference of the fit, either the reduction in radial internal clearance of the bearing or the axial displacement of the inner ring on its tapered seat is used.

Suitable methods for mounting self-aligning ball bearings with tapered bore are:

• easuring the clearance reduction.
• easuring the lock nut tightening angle.
• easuring the axial drive-up.

Detailed instructions for a selected bearing can be found at skf.com/mount.

Mounting bearings with a tapered bore – Measuring the clearance reduction

When mounting basic design self-aligning ball bearings with the relatively small Normal radial internal clearance, it is generally sufficient to check clearance during the drive-up by turning and swivelling out the outer ring. When the bearing is properly mounted the outer ring can be easily turned but there should be a slight resistance when the outer ring is swivelled out. The bearing will then have the requisite interference fit. In some cases the residual internal clearance may be too small for the application, and a bearing with C3 radial internal clearance should be used instead.

Detailed instructions for a selected bearing can be found at skf.com/mount.

Mounting bearings with a tapered bore – Measuring the lock nut tightening angle

The procedure for using the nut tightening angle (fig 1) represents an easy method for mounting self-aligning ball bearings with a tapered bore correctly. Recommended values for the nut tightening angle a are provided in the table.

Nut tightening angle a

Before starting the final tightening procedure, the bearing should be pushed up on the tapered seat until the bore of the bearing or sleeve is in contact with the seat on the shaft around its whole circumference, i.e. the bearing inner ring cannot be rotated relatively to the shaft. By then turning the nut through the given angle a, the bearing will be pressed up the tapered seat. The residual clearance of the bearing should be checked by turning and swivelling out the outer ring.

Then unscrew the nut, place the locking washer in position and tighten the nut firmly again. Lock the nut by bending one of the locking washer tabs into one of the nut slots.

Detailed instructions for a selected bearing can be found at skf.com/mount.

Mounting bearings with a tapered bore – Measuring the axial drive-up

Mounting bearings with a tapered bore can be done by measuring the axial drive-up of the inner ring on its seat. Recommended values for the required axial drive-up “s” for general applications are provided in the table.

The most suitable method in this case is the SKF Drive-up Method. This mounting method provides a very reliable and easy way to determine the starting position for a bearing from which the axial displacement is to be measured. For that, the following mounting tools (fig 1) must be used

• an SKF hydraulic nut of the HMV .. E design
• an appropriate hydraulic pump
• a pressure gauge, appropriate to the mounting conditions
• a dial gauge.

SKF Drive-up method, mounting tools

Applying the drive-up method, the bearing is pushed up its seat to a defined starting position (fig 2) using a given oil pressure (corresponding to a given drive-up force) in the hydraulic nut. In this way, part of the desired reduction in radial internal clearance is achieved. The oil pressure is monitored by the pressure gauge. The bearing is then driven up from the defined starting position through a given distance to its final position. The axial displacement “ss” is accurately determined using the dial gauge mounted on the hydraulic nut and can be calculated for individual bearings at skf.com/mount where also detailed mounting instructions are available.

Axial drive-up distance

Note The axial displacement “ss” is not the same distance as the distance “s” in the table.

Self-aligning ball bearings | Mounting bearings with a tapered bore