## Selection of Rolling Element Bearings – Part 1

written by: kkaarthic • edited by: Lamar Stonecypher • updated: 5/4/2010

This article deals with the important terminologies we need to know about for the selection of a rolling element bearing. These terms like axial and radial loads, Static Load carrying capacity, Dynamic Load carrying capacity, etc are explained in detail.

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Rolling Element bearings are quite unique. These bearings in various types, ranges and sizes are manufactured and available as catalogued products from various manufacturers. All that we need to know is certain parameters which will help us to select a suitable bearing, which could be procured from the shelf of a bearing shop quite easily. To select a bearing suitable for our application we need to have the following information which will help us in the selection of a bearing.

These are some common things that need to be in one’s mind before proceeding with the selection of a bearing.

1. The bearing is a machine element just like other elements like shaft, gear, etc., in a machine system

2. The bearing always requires a shaft to be mounted upon and a casing to hold its outer diameter. This is necessarily required holding the bearing in its place.

3. The bearing is a highly sensitive element requiring good amount of knowledge by anyone for its selection and use. Proper care is to be ensured during selection, procuring, mounting and running.

Parameters required for the Selection of a Bearing:

1. Radial Force and Axial Force: Click here to see where these forces act on the bearing. The bearings act as support points to the shaft which rotates. Any force that is created in the shaft due to the mounted elements on the shaft like gears, blades, etc tends to generate forces. These forces in turn are conveyed from the shaft to the housing via the bearing. Hence it is important that the bearing is able to withstand this load for its survival.

a. The radial force denoted by (Fr) acts in the radial direction to the bearing. See above Figure. A good example for the radial force would be the self weight of the shaft.

b. The Axial Force denoted by (Fa) acts inline with the shaft axis. See above figure. A good example to make you understand on the axial force would be – Just try walking upwind you would feel the force of the wind against you this is the axial force and the ground that supports you beneath takes care of the radial force of your self weight.

2. Speed of the Shaft: The speed of the shaft is required in order to estimate the life of the bearing. Moreover each type of bearing has its own restrictions related to the maximum speed in which it can run.

3. Lubrication: The lubrication is an important area. We really must know the type of lubrication the bearing is going to run in like sump lubrication, forced lubrication, Oil Mist Lubrication, etc. We will look more in detail on the lubrication aspects of the bearings in the forthcoming articles.

4. Operating Temperature: The operating temperature of the bearing is very much required. Special considerations like operation in below zero degree temperatures, high temperature operations like the bearings used in turbines, etc. are required to be specifically known by the bearing selector.

#### Selection of Rolling Element Bearings

This article deals with the important terminologies we need to know about for the selection of a rolling element bearing. These terms like axial and radial loads, Static Load carrying capacity, Dynamic Load carrying capacity, etc are explained in detail.