SKF - Spherical Plain Bearings and Rod Ends

Design of bearing arrangements
5. Axial displacement of non-locating bearings
A non-locating bearing provides radial support
only and must always be able to be displaced
axially († fig. 5). This is normally achieved by
selecting a loose fit for one of the bearing rings,
generally the inner ring of a spherical plain
bearing. Reasons include the following:
• The shaft seat can be easily and economically
hardened and ground to facilitate axial displacement.
The hardness of the shaft should
be at least 50 HRC.
• The outer rings of most spherical plain
bearings are axially fractured at one or two
positions, or are radially split. This can make
axial displacement difficult, if not impossible.
• The housing bore should be protected against
wear.
Surface finish of seats
The recommended surface roughness for bearing
seats is in accordance with ISO 4288:1997.
Axial displacement
ISO shaft and housing tolerance classes
Fig. 5
Fig. 6
• for shaft seats Rz ≤ 10 μm
• for housing bore seats Rz ≤ 16 μm
Recommended fits
Only a limited number of ISO tolerance classes
are appropriate for spherical plain bearings.
Fig. 6 shows schematically the relative positions
of these in relation to the bore and outside
diameter of the bearings. The recommended
tolerance classes for
• the shaft seat are provided in table 1
• the housing bore are provided in table 2
These recommendations are based on the
considerations described above and have been
confirmed in a wide variety of bearing applications.
The ISO tolerance limits are listed in
• table 3 on page 74 for shafts
• table 4 on page 74 for housing bores
To facilitate the calculation of the minimum and
maximum values of the theoretical interference
or clearance, the standardized bearing bore
diameter deviations (Δ dmp ) and the bearing outside
diameter deviations (Δ Dmp ) are listed in
tables 3 and 4.
+
0
+
0
H11
H7 J7 K7 M7 N7
g6 h6 k6 m6 n6
72