Measuring Bearing Radial Clearance
Measuring the radial clearance of a bearing is an important maintenance task. Many bearing failures can be attributed to incorrect radial clearance, which leads to excessive stress on the bearings. Since the radial clearance of a bearing influences the load capacity and operating temperature of the bearing, it is critical that the radial clearance be within the specified tolerance established for the bearing through engineering analysis.
This tutorial will provide a summary of the appropriate procedures for measuring radial clearance in a bearing assembly.
Understanding Radial Clearance
Radial clearance is the radial height difference between the inner and outer races of a bearing. It is usually expressed in thousandths of an inch or in micrometers.
Factors Affecting Radial Clearance
Radial clearance in a bearing assembly is affected by several factors:
· Manufacturing tolerances and finish of the inner and outer races
· Grease and lubrication
· Assembly contact between inner and outer races and rollers
· Dynamic load of the raceway
· Environmental temperature
Measuring Radial Clearance
A proper radial clearance measurement is taken with a micrometer that has a 1-2 inch anvil.
The first step is to clean the bearing assembly and lubricate it with a light oil or grease. Next, the micrometer should be attached to the inner race of the bearing, and the micrometer anvil should be resting on the outer race. The micrometer should be adjusted to contact the outer race of the bearing and then the reading should be taken and recorded. The micrometer should then be adjusted and the process repeated at least four more times in 90 degree increments. This will ensure that an accurate average of the radial clearance is recorded.
It is important to note that the micrometer anvil should not be touching the bearings rollers. If the anvil is touching the rollers, the bearings radial clearance will be falsely increased.
Next, the radial clearance should be measured on the space between the roller and the outside of the bearing raceway. This is accomplished by using a feeler gage. If the feeler gage does not move freely, then it is an indication that the space is too small and the bearings radial clearance is too great.
Finally, the average bearing radial clearance should be compared to the engineering specifications for the particular bearing. If it is not within the appropriate tolerance, the bearing should be replaced.
Conclusion
Measuring the radial clearance of a bearing is an important maintenance task that should be done regularly to ensure proper bearing performance and prevent premature bearing failure. With the proper procedures and measurements, bearings with the correct radial clearance can be identified and maintained.
