The Bearing Housing

The housings are manufactured with flat mounting surfaces that simplify the installation of the unit. In pillow blocks, the flat surface is a straight footed support at the base of the housing — the mounting surface of a pillow block is parallel to the axis of the shaft. Conversely, in flange units, the shaft runs at a 90° angle to the mounting surface to which the unit is attached.

In addition to the different types of housings available, another major option exists. The housing may be manufactured to allow for the relubrication of the bearing. A housing without this option is described as being maintenance-free. A housing with this option is described as a relubricatable, or relube, type unit.

While the maintenance-free housing is made with no provision for regreasing the bearing insert, the relubricative-type housing is drilled and tapped (threaded) to accept a grease fitting. In the U.S. the fitting typically is available in inch sizes; outside the U.S. the fitting would come in metric sizes. In packaging, the fitting may be included within the carton but not assembled in order to prevent shearing during shipment. In this case, the drilled hole is plugged to prevent bearing contamination. Most units are packaged fully assembled.

The drilled hole leads through the housing to a circumferential grease groove which has been machined along the housing’s bore. This groove is slightly offset to either side of the outer ring’s width, a variation dependent on the manufacturer’s specifications. When ordering a replacement insert bearing and when installing it within the housing, it is important to identify the small offset holes in the outer ring of the insert bearing and to ensure that they are positioned on the same side as the groove machined in the housing. Failure to position the bearing properly means that the lubricant will not be able to flow into the bearing.