Some concepts of bearings
 
 
 
1. Bearing axis
 
 
 
The theoretical rotation axis of rolling bearing is the axis line of inner ring for counter bearing and the axis line of shaft ring for thrust bearing.
 
 
 
2. Inner ring (shaft washer) axis
 
 
 
The axis line of the inner cylinder or the inner cone of the basic cylindrical or conical hole of the inner ring (axial ring).
 
 
 
3. Outer ring (housing washer) axis
 
 
 
If the outer surface of the outer ring is cylindrical, the axis line of the outer cylinder of the outer surface is the axis line of the outer ring. If the surface is basically spherical, the axis line of the outer ring is the line perpendicular to the reference end face of the outer ring through the center of the outer sphere of the ferrule.
 
 
 
4. Cone (cup) axis
 
 
 
The axis of the inner ring (outer ring) of a tapered roller bearing.
 
 
 
5. Radial plane
 
 
 
The plane perpendicular to the axis line and parallel to the cutting plane of the reference end face of the ferrule or the back face of the gasket can be considered as a radial plane.
 
 
 
6. Radial direction
 
 
 
The direction through the axis in the radial plane.
 
 
 
7. Axial plane
 
 
 
A plane containing the axis.
 
 
 
8. Axial direction
 
 
 
Parallel to the bearing axis. The direction perpendicular to the cutting surface of the reference end face of the ferrule or the back face of the washer can be considered as the axial direction.
 
 
 
9. Radial (axial) distance
 
 
 
The distance measured radially (axially).
 
 
 
10. Contact angle (nominal contact angle)
 
 
 
The angle between the plane perpendicular to the bearing axis (radial plane) and the resultant action line (nominal action line) transmitted to the rolling element through the bearing rings or washers.
 
 
 
11. Nominal contact point
 
 
 
When the bearing parts are in the normal relative position, the contact point between the rolling body and the raceway surface.
 
 
 
12. Reference face of a ring (a washer)
 
 
 
The bearing manufacturer designates the end face of the ferrule (washer) as the datum plane, which can be used as the datum of measurement.