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How to Install a Mounted Bearing Unit

We get a lot of questions on how to properly install a mounted bearing unit. So here's some info to hopefully help you have a successful bearing installation.

Mounting Instructions

Proper mounting of a ball bearing unit is critical to a units performance. Failure to follow accepted mounting practices may result in poor performance and short bearing life.

Good engineering and design practice does not recommend the application of more than two bearings supporting any one shaft. Where more than two bearings are used to support the same shaft, it is possible to induce heavy bearing overloads. I cases where a larger shaft cannot be introduced then using more then two bearings on a shaft is not out of the question but is not looked at as optimal. In these cases, extreme care must be taken to line up bearings in both vertical and horizontal planes. When the recommended two bearings are used, alignment is not as critical. Self-aligning mounted bearing units will compensate for minor differences in mounting structure.

For best results, use turned and ground shafts that are free of rough spots and burrs. If an old shaft is used, mount the bearing units on a relatively smooth and unworn section.

Prior to mounting, clean both the shaft and the bearing bore. Coat the shaft with a small amount of oil. Slide the bearing unit on the shaft. Do not hammer the ends of the inner race. If necessary to apply some force in mounting, use a soft metal bar or pipe against the inner race only. Tap the bearing unit into place.

Mounted units with set screws:

Tighten the two set screws securely to lock the bearing to the shaft. In applications where the bearing is subjected to heavy vibration, shock loads, or heavy thrust loads, it may be desirable to file the shaft flat or drill the shaft slightly in the area where the set screws will contact.


Set Screw Size






















Mounted units with eccentric collar:

The eccentric locking collar uses an extended inner ring of the bearing that contains a channel eccentric to the shaft, and a matching channel in a collar that fits over the inner ring extension. The unit is secured to the shaft by rotating the collar relative to the inner ring. When this is done, the force introduced to the rotation is transmitted as holding force perpendicular to the shaft. A setscrew is supplied to prevent loosening of the collar during reverse rotation. This is a precautionary practice, and does not compensate for frequent reverse rotation. Manufacturers agree that eccentric locking collars should not be used for bidirectional applications

Most of our mounted ball bearings have the ability to be re-lubricated. But just how often do you have to put that brass grease fitting to good use? Depends on a lot of conditions. Here is some info to help extend your bearing life through lubrication.



The proper lubrication of ball bearing units is critical in order to attain maximum bearing life expectancy. Our ball bearing units are pre-lubricated and do not need to be lubricated prior to use. They should be re-lubricated periodically, depending on the environment the bearing is exposed to.  Use the following table as a general guide. Experience will determine the best interval for each specific application.


Operating Conditions

Bearing Temperatures

Grease Interval


32F to 120F

6-12 Months


120F to 150F

1-3 Months


150F to 200F

1-4 Weeks


32F to 150F

1-4 Weeks


150F to 200F

Daily-1 Week


32F to 200F

Daily-1 Week


The amount and type of lubricant used will affect bearing life. Lack of lubrication can lead to premature surface fatigue failures of the balls and races. Over lubrication can damage seals and result in premature failure from contamination due to inability of damaged seals to keep foreign material out of the bearing. Also, too much grease will cause excessive drag and over heat the bearing from the extra friction.

When lubricating bearing add grease slowly while the shaft is rotating. When the first sign of grease appears at the seals, the bearing will contain the correct amount of lubricant.

Bearings should not run in steady operation over 200F and should not exceed 225F for intermittent operation.

Just what is a Self Aligning Bearing?

Our mounted ball bearing units consist of two main components, a single row deep grove ball bearing insert and a cast iron bearing housing. The bearing insert has a rounded outer diameter that when mounted in the cast iron housing fits into the equally rounded inside of the housing. Because both the housing and the bearing have equally rounded contact points the insert bearing will pivot inside the bearing housing to accommodate misalignment of the shaft, vibration of the mounting surface/shaft and variance in the mounting of other bearings down the shaft. The tolerance between the bearing and the housing is so tight that it is not possible to adjust the angle with your hand you must bolt the bearing down or place it in a vice and use a pry bar or the shaft.

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