Internal Radial Clearance Classes

Three classes of internal radial clerance for tapered bore bearings are commonly in use: CC9, CC0, and CC1.
It depends on the operating conditions which class is most suitable.
NSK has chosen to make CC0, a well-balanced clearance, its standard internal radial clearance class because of
its advantages in terms of ease of mounting and spindle accuracy.

NSK's recommended clearance

・CCO clearance

With the upper limit of CC1 and the lower limit of CC9 omitted, this class offers medium radial clearance. Its range is also smaller than that of CC1.
As it is the easiest-to-use for customers who target this range, it is the recommended clearance offered for CRB with tapered bore.

・CC9 clearance

The bearings of this class are produced with the lowest internal clearance of the three classes.
Therefore, the bearing needs to be pushed onto the shaft only a short distance,
which helps to avoid the negative influence of interference on bearing accuracy or deformation of the shaft bore.
However, in the case of the bearing's internal clearance after manufacture being at the lower end of the range,
only a small movement is required to drive the bearing onto the tapered shaft to achieve the required clearance.
Depending on the load and especially in high-speed operation, pushing the bearing too short a distance onto the shaft may cause
creep damage between the shaft and the inner ring of the bearing.

・CC1 clearance

Traditionally, this internal clearance class has been the most popular.
There is no danger of creep damage, because the bearing will necessarily be pushed onto the shaft by a certain amount.
However, in the case of the bearing's internal clearance after manufacture being at the high end of the range,
the bearing will be pushed further onto the tapered shaft.
This may be detrimental to bearing accuracy or cause deformation of the inside shaft bore.
Especially when a thin hollow shaft has a large bore diameter, this bore diameter may easily shrink.