Load, sliding velocity, operating temperature are primary factors in determining the friction in plain bearings. Friction is also influenced by the roughness of the surface on which the bearing runs, the degree of contamination and the lubrication conditions.

The range of the friction coefficient µ for each bushing, thrust washer and stripe material is provided under the relevant bearing data sections:

Guideline values for the coefficient of friction µ of PTFE composite plain bearings

Using PTFE composite bearings as an example for the coefficient of friction µ under different operating conditions, the lowest values are normally obtained where there are high specific loads and low sliding velocities (diagram 1). Under particularly unfavourable operating conditions, like light loads, high velocities or inadequate surfaces, the maximum guideline values may be exceeded. The coefficient of friction µ for PTFE composite bearings increases at temperatures above +100 °C.

Similar values are found for the POM composite material, but the presence or constant supply of lubricating fluids serves to decrease friction.

Stick-slip effects are negligible for PTFE and POM bushings.

PTFE bushings typically have a running-in period (Bushing designs and variants).

Friction behaviour of other materials

For information about friction behaviour of other materials, contact the SKF application engineering service.

SKF logo