For most types of rolling bearings installed in the bearing housing of a rolling mill, end covers are required to compress the outer ring end faces of the bearings, such as four-row cylindrical roller bearings, four-row conical roller bearings, etc., in order to prevent axial movement or rotation of the outer ring of the bearing or the bearing components in the bearing housing.

Usually, the gap after the bearing outer ring is compressed is adjusted by using a gasket between the end face of the bearing outer ring and the flange of the end cover, so that the bearing outer ring can be axially compressed and the pre-tightening force can meet the specified requirements. 

The commonly used materials for gaskets include compressible soft gaskets, such as paper gaskets and rubber gaskets (which can be made on-site or customized by manufacturers); there are also reusable steel gaskets (small-sized ones are integrated, while larger ones can be segmented and assembled on-site).

Paper gaskets, made on-site, have relatively small compression, and need to be re-made after damage.

Rubber gasket, which can be made on-site or customized in the factory. It has a relatively large compression rate, usually compressing by 20% to 40%. The thickness of the gasket is calculated based on the compression ratio and the gap between the end cover and the bearing seat. After the end cover bolts are tightened, the gap needs to be measured to verify the value compared with the original value before tightening.

Steel gaskets can be reused. Select the gaskets in a one-to-one ratio. There is no need to consider the compression ratio of the gaskets. 

The bearing is installed into the bearing housing. Although the outer ring of the bearing has a clearance fit, sometimes the components of the bearing do not fit tightly into the bearing housing. The end face of the outer ring of the bearing may be slightly higher than the required size specified in the drawing. At this time, the gap between the end cover and the bearing end face may not be a true gap. The end cover should be tightened without any spacer, and the bearing outer ring should be pressed in place before measuring the gap size. The bolts should be tightened symmetrically, and the torque force should not be too large to avoid deformation of the bearing or the end cover.

Four slots are cut at the 90-degree position to facilitate the verification of the gap between the compression end cover after installation. 

When choosing the thickness of the steel gasket, it is generally the measured gap value minus (0, -0.05) to ensure that the end cover can be tightly pressed and the steel gasket can ensure that after tightening the bolts, a uniform torque force is distributed on the bearing surface.

If installing a tapered roller bearing with an outer retaining ring, when using soft gaskets, it is advisable to use a torque wrench to avoid compression of the internal clearance of the bearing or excessive deformation due to overload.