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By Team BC on 19 February 2018 in Bearing Corporation Blog





Radial Internal Clearance

The radial internal clearance of a ball bearing affects life, noise, vibration and heat generation.  It is important to select the appropriate internal clearance for each application.

The three types of internal clearance of a ball bearing are radial clearance, axial clearance and moment clearance.

Radial internal clearance decreases when a ball bearing is fitted to either a shaft or housing with interference.

The fits and temperature affect the radial internal clearance.  Therefore, actual application conditions need to be reviewed when radial internal clearance is selected.

Radial Clearance (Gr)

Figure 1

The displacement generated by moving the outer ring in the radial direction while securing the inner ring.

Axial Clearance (Gt)

Figure 2

The displacement generated by moving the inner ring in the axial direction while securing the outer ring.

Moment Clearance (θ)

Figure 3

The angular displacement generated by tilting the inner ring in the axial direction while securing the outer ring.

The operating clearance or preload in a bearing influences, among other things, the friction, load zone size and fatigue life of a bearing. For general applications, the operating clearance range should be within the recommended zone.

What are C2, C3, C4 and C5 bearings?
C3, C4 and C5 bearings are bearings that have an additional internal radial clearance to cope with high speed environments where excess heat is generated. They are not suited to environments where critical alignment is required from the onset e.g. Where blades and cutters are set up to each other. Applications like motorcycle wheels or bicycle wheels do not require C3 rated bearings. Unless the bearing you are replacing specifically says C3 on it then you should not replace it with a C3 bearing, C3 Bearings are loose to the feel from new and often people complain at the quality of the bearing being poor and having more movement than the one they are replacing. C4 and C5 are even looser still than C3 clearance bearings. This is the characteristic of these higher than normal clearance bearings marked C3, C4 and C5.
C2 marked bearings have less clearance internally than standard bearings and should only be used in applications that specify C2 clearance.

Selecting initial internal clearance and Selecting preload describe the influencing factors that must be considered and provide the methods by which you can calculate the initial internal clearance needed to achieve the degree of clearance/preload required by your application.

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