A bearing by definition is a part of a machine that bears friction, especially between a rotating part and its housing. The architectural definition is a structural part that supports weight. A ball bearing is a rolling element bearing that uses balls to maintain separation between the inner races. Ball bearings are typically used between cantilever and rotary shafts to transfer axial or radial load. Ball bearings need to be retained in three directions, radial, axial, and circumferential in relation to its housing and a shaft. The radial and circumferential direction retention is mainly based on a concern on fit tolerance selection. The remaining “axial direction” retention cannot be solved by press fitting of the bearing. There are several ways to axially retain bearings and what better way to explain them than with application examples. The examples we will discuss are specifically designed for low to medium speed bearings.
Bearing Mounting/Retaining Methods
Bearing mounting components:
- Bearing retaining collar
- Bearing shaft screw
- Bearing Nut
- Bearing Spacer
- Bearing end-cap
Example 1 Mounting method for belt tension adjusting idler pulley bearing
The idler pulley is mounted with a cantilever pin. This example uses a nut tightened cantilever type. A bearing retaining collar is used to fix the idler pulley bearing. A washer is placed between the bearing and the collar to provide an ample access to the collar’s tightening screw. The washer outer diameter should match the outer diameter of the bearing’s inner ring.
Example 2 V-groove idler pulley mounting with a bearing end cap
A flanged screw mounted cantilever pin is used. It is important to note that the bearing end cap needs to match the outer diameter of the cantilever pin shaft.
Multiple Bearing Retaining Methods
Here, an axial mounting method of bearings is explained using a linking mechanism with bearings mounted on two T shaped bearing holders.
In this example, three bearing retaining methods are utilized. A metal washer is used on the tightening side of the cantilever pin to hold against the inner ring of a radial bearing. A bearing spacer is placed between the link arm and a bearing to support the link’s rotation motion. The bearing on the opposite side is fixed to the cantilever pin shaft by its inner ring with a bearing end cap.
Examples of Rotating Shaft Retention
This is an example of rotating shaft retention using a bearing holder set (T-shaped two bearing type, or bottom mount two bearing type) and bearing nuts with anti-loosening set screws or bearing lock nuts. Loosening of the bearing nut is prevented by use of a set screw and a set piece made of copper alloy. The set piece made of soft copper alloy is first inserted in a screw hole, and a set screw is tightened to crush the soft alloy piece on the shaft thread to prevent the bearing nut from loosening.
This is an example using bearing holding pins also called bearing shaft screws. A bearing holding pin holds against the inner ring outer diameter from the end side, and a collar from the inside is pressed against the inner ring outer diameter of the bearing from the other side to fix the bearing to the shaft.
There are a variety of ways to retain bearings in your application but it is equally important to note the tolerances of bearings. For a review, check out this post on Rotary Bearing Fits and Tolerances. Also, don’t forget the importance of maintaining your rotary bearings. Proper maintenance techniques can prolong the life of your products and machines and prevent premature and unscheduled shutdowns Check out the post on easy maintenance tips for your rotary bearings here.
What are some ways you retain your bearings? What have you found to be the best methods for your applications? Share in the comments below!