Steel/steel and steel/bronze sliding contact surface combinations, requiring maintenance

The basic rating life for initial lubrication only, can be calculated using

Gh = b1 b2 b3 b4 b5 330 / p2,5 v

The basic rating life for bearings with regular relubrication, can be calculated using

GhN = Gh fβ fH


GN = 60 f GhN

The frequency of relubrication can be calculated using

H = Gh / N

Gh=basic rating life with initial lubrication only, operating hours [h]
GhN=basic rating life with regular relubrication, operating hours [h]
GN=basic rating life with regular relubrication, number of oscillations
H=frequency of relubrication (diagram 1)
b1=load direction factor
  • for constant direction load b1 = 1
  • for alternating direction load b1 = 2
b2=temperature factor (table 1)
b3=sliding factor (diagram 2)
b4=velocity factor (diagram 3)
b5=factor for angle of oscillation (diagram 4), refer to Note
p=specific bearing load [N/mm2] (for values of p < 10 N/mm2 use p = 10 N/mm2)
v=mean sliding velocity [m/s]
fβ=factor depending on the angle of oscillation (diagram 5), refer to Note
fH=factor depending on the frequency of relubrication (diagram 6)
f=frequency of oscillation [min–1]
N=relubrication interval [h]


SKF manufactures heavy-duty spherical plain bearings with the multi-groove feature in the outer ring (→ Bearings and rod ends requiring maintenance). The extra large grease reservoir in those bearings extends relubrication intervals and bearing service life, especially in applications where there are constant direction loads (fig. 1).

These advantages are considered in the calculation of the basic rating life by the coloured regions in diagrams for angle of oscillation b5 (diagram 4) and diagrams for factor fβ (diagram 5). The values of these two factors in the upper limit of the coloured area may be used for bearings with the multi-groove system.
If the basic rating life requirement is not met, the relubrication interval N should be shortened, or a larger bearing or rod end should be selected.
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