Clearance
What is clearance ?
Bearing Internal Clearance is described as the distance by which, Outer ring of the bearing can be displaced relative to the Inner ring under no measuring load.
Why Clearance is Required?
A small amount of clearance is always required to avoid metal to metal contact in bearings between moving surfaces. Therefore before selecting a bearing for a particular application one must look for other surrounding influences. Different clearances are generally required in bearings due to following reasons:-
To enable the use of interference fits which significantly reduces the clearance when applied.
To allow for the expansion of the shaft or shrinkage of the housing under temperature influence.
To allow for the use of housings and shafts produced in materials other than steel that may have different rates of thermal growth such as Aluminum.
To accommodate nominal misalignment tolerances on bearings and mating parts.
What are different clearance grades ?
Clearances grades are selected based on, the bearings interference fit on the shaft.
C1 --- Clearance lesser than C2
C2 --- Clearance Lesser than Normal
CN --- Normal Clearance
C3 --- Higher than CN
C4 --- Higher than C3
As per ISO, if nothing is mentioned in the bearing designation, that means it is having a Normal Clearance. (CN).