How Can a Tolerance Ring Improve Bearing Performance?
• Compensate for thermal growth/contraction between a bearing and housing
• Compensate for bearing misalignment
• Relaxing housing tolerances can reduce production costs
• Easily mount bearings where an interference fit is undesirable
• Infinite rotational indexing of parts prior to assembly
Compensate for Thermal Growth
Content to come
Compensate for Bearing Misalignment
When press fit bearing pairs are misaligned due to non-collinear housing and bore hole center axes, additional radial loads, moments and vibrational forces are exerted on the shaft and bearings. If the misalignment is significant, bearings will fail prematurely.
Tolerance rings are more forgiving than a pure press fit. Depending on the spring rate (K) of the tolerance ring and amount of center axes offset, the corrugations’ spring-like characteristics will allow for improved alignment and longer bearing life.
The Ideal Fit-Up
A precision ground housing and a snug fit will only be ideal if there is no bearing misalignments during installation and if there are no thermal expansion requirements for the ball bearing to float in the housing.
A Tolerance Ring provides the ideal fit up between a ball bearing outer ring and its housing bore. Tolerance Rings will compensate for expansion and minor misalignment. The outer ring will fit snuggly between the Tolerance Ring and the housing bore.
Housing Design Requirements
Using a 6203 ball bearing as an example…the ball bearing outside diameter tolerance is .011 mm or .00045 in. The internal clearance of this bearing in the free state is .003-.018 mm or .0001-0007 in. The recommended standard steel housing bore tolerance for this popular ball bearing is +.016 mm or +.0006 in.
Depending on the complexity of the housing, in most cases a grinding operation will be required to ensure adequate support for the ball bearing outer ring. Any out of roundness or housing wall variations could adversely affect ball bearing performance and life. Without a tolerance ring there is no place for the housing irregularities to go, but into the bearing.
In the worst case, using a tolerance ring would require only a machining operation. The recommended housing bore tolerance with a tolerance ring increases to .010 mm or .004 in.
Let’s add a section about precision machining costs as well