Static Safety Factor

The basic static load rating C0 refers to the static load with constant direction and magnitude, under which the calculated contact stress in the center of the contact area between the roller and the raceway under the maximum load is 4000 MPa. (If the contact stress exceeds this level, it will affect the rotation.) This value is indicated as "C0" in the dimensional tables. When a load is statically or dynamically applied, it is necessary to consider the static safety factor as shown below.

fS Static safety factor in relation to C0 (see Table1 )
C0 Basic static load rating (kN)
P0 Radial load (kN)

The permissible load (F0) indicates the permissible value of the applied load determined by the strength of the stud section of the Cam Follower. Therefore, it is necessary to consider the static safety factor fM against F0 as well as fS .

fM Static safety factor in relation to F0 (see Table1 )
F0 Permissible load (kN)
P0 Radial load (kN)
  • * The minimum value for the static safety factor is based on the presumption of appropriate lubrication and optimal conditions for mounting and assembly. It is not possible to calculate the effect on internal loads that may be caused by improper mounting, deformation of mounting components, or the like. Please take all necessary action to ensure safety.
Table1 Static Safety Factor (fS , fM )
Load conditions Lower limit of fS
and fM
Normal load 1 to 2
Impact load 2 to 3

Calculating the Nominal Life

The nominal life (L10) is obtained from the following formula using the basic dynamic load rating (C) and the load applied to the cam follower (PC ).

L10 Nominal life (rev.)
C Basic dynamic load rating * (kN)
PC Radial load (kN)

Calculating the Modifi ed Nominal Life

During use, a cam follower may be subjected to vibrations and shocks as well as fluctuating loads, which are difficult to detect. In addition, the operating temperature will have a decisive impact on the service life. Taking these factors into account, the modified nominal life (L10m) can be calculated according to the following formula (2).

Modifi ed factor α
α Modified factor
fT Temperature factor (see Fig.1 )
fW Load factor (see Table2 )
Modified nominal life L10m
L10m Modified nominal life (rev.)
C Basic dynamic load rating * (kN)
PC Radial load (kN)
  • * The basic dynamic load rating (C) of the cam follower shows the radial load under which the nominal life is 1 million revolutions when a group of identical cam follower units independently operate, assuming a constant direction and magnitude of the load. This value is indicated in the specification tables.

Calculating the Service Life Time

When the nominal life (L10) has been obtained, the service life time (Lh) is obtained from the following equation.

For Linear Motion
Lh Service life time (h)
L Nominal life
D Bearing outer diameter (mm)
S Stroke length (mm)
n1 Number of reciprocations per minute (min-1)
  • Note) The normal service temperature is 80℃ or below. If the product is to be used at a higher temperature, contact THK.
For Rotary Motion
D1 Outer ring contact average diameter of the cam (mm)
n Revolutions per minute of the cam (min-1)
Table2 Load Factor (fW )
Condition fW
Smooth motion without impact 1 to 1.2
Normal motion 1.2 to 1.5
Motion with severe impact 1.5 to 3