Bearings - Fitting of bearings

Fitting of bearings

When a ball bearing is used, it is always fitted to a shaft and/or a housing bore. Fit is a value of tightness between the shaft and bearing bore, as well as the fit between the housing and bearing outer diameter, when the bearing is installed.
he purpose of selecting the proper fitting condition is to suppress vibration during rotation, and to secure the inner ring and shaft of the ball bearing, and the housing and outer ring, to prevent slipping (creeping). When creeping occurs, abnormal heat generation and wear powder are generated due to sliding wear.

Abnormal heat generation accelerates the deterioration of grease, and wear particles enter the bearings, causing vibration and deterioration. It is necessary to choose a proper fit for each application because improper fits can not only degrade the bearing performance, but also they could cause seizure due to heat generation and premature failure. Additional info

Preparation prior to mounting:

Wait until just before mounting before removing the bearings from their packaging to prevent contamination and rust. Since the anti-corrosion oil covering bearings is a highly capable lubricant, the oil should not be cleaned off if the bearings are pre-lubricated, or when the bearings are used for normal operation. However, if the bearings are used in measuring instruments or at high rotation speed, the anti-corrosion oil should be removed using a clean detergent oil. After removal of the anti-corrosion oil, bearings should not be left for a long time because they rust easily.

Inspection of shafts and housings

Clean up the shaft and housing to check whether it has flaws or burrs as a result of machining.
Be very careful to completely remove lapping agents, casting sands, and chips from inside the housing.
Next, check that the dimensions, forms, and finish conditions of the shaft and the housing are accurate to those specified on the drawing. The shaft diameter and housing bore diameter should be measured at the several points.
Furthermore, fillet radius of shaft and housing, and the squareness of shoulders should be checked.

Methods of fitting bearings