Bearing internal clearance is defined as the total distance through which one bearing ring can be moved relative to the other in the radial direction before mounting.
The internal clearance of a bearing under operating conditions is usually smaller than the bearing's initial clearance before being installed and operated. This is due to several factors including bearing fit, the difference in temperature between the inner and outer rings, etc. As a bearing's operating clearance has an effect on bearing life, heat generation, vibration, noise, etc.; care must be taken in selecting the most suitable operating clearance.
The bearing's life is theoretically maximum when operating clearance is slightly negative at steady operation. In reality it is however difficult to constantly maintain this optimal condition. If the negative clearance becomes enlarged by fluctuating operating conditions, heat will be produced and life will decrease dramatically. Under ordinary? circumstances you should therefore select an initial internal clearance where the operating clearance is slightly larger than zero.For ordinary operating conditions, use fitting for ordinary loads. If rotational speed and operating temperature are ordinary, selecting normal clearance enables you to obtain the proper operating clearance.
The radial clearance is subdivided into groups by suffixes CN to C5
|CN||Normal CN is not included in bearing designation|
|C2||Smaller than CN|
|C3||Larger than CN|
|C4||Larger than C3|
|C5||Larger than C4|
Radial Internal Clearance of Miniature and Extra-small Ball Bearings
Radial internal clearance of deep groove bearings
|Bore Diameter||C2||Normal(CN)||C3||C4||C5||For Electric Motor|