A dual bearing structure for supporting the rotor shaft of a rotatable machine such as a turbocharger includes antifriction bearings of the inclined contact ball type which accommodate radial forces and also axial forces acting in one direction on the shaft and a plain thrust bearing located adjacent the antifriction bearings which accommodates axial forces acting in the opposite direction. The fixed ring of the thrust bearing includes radial oil guide slots and lubricating oil for the bearings admitted into the bearing housing forms a rotatable ring of oil which owing to the action of centrifugal force passes from the antifriction bearing into the oil guide slots in the fixed ring of the thrust bearing.
