Introduction

Bearings come in a seemingly endless array of sizes and configurations, each tailored to meet the specific demands of a particular application. The objective of this guide is to provide a basic introduction to a specific group of bearings—mounted unit bearings—commonly referred to as pillow block and flange bearings.

This family of bearings is distinctive because the bearing unit is considered as a product item, when in fact it actually consists of a ball or roller bearing installed within a separate fixture called the housing. These housings are most commonly made of cast iron but may also be made of other metals or nonmetallic materials. The housing provides rigidity and secure positioning for the bearing within the application. It also simplifies the task of replacing the bearing, as the housing and bearing can be replaced as a complete unit. Bearing units also offer the additional advantage of being an "off the shelf" housed bearing product.

Also covered in this guide, in addition to housings and their features, are a number of the other product design features, attachments and special options that make these versatile bearings a basic item in many applications and industries.

While it’s not possible to cover every aspect of bearing unit design technology, we will attempt to provide you with a basic understanding of the principles of how they have been designed and how they function. Whatever your level of familiarity, we hope to further your understanding of mounted units, or that the information provided will serve as a refresher course for you or assist you in training others.