An orbiting mass oscillator for generating vibratory energy has an unbalanced rotor which is rotatably driven around the wall of a housing. Oil is fed to the housing with a longitudinal flow therein to provide a thick oil film between the rotor and the housing wall, thereby providing cushioning therebetween which dampens the effects of sharp jolting forces on the oscillator in situations such as where the oscillator is used to drive a drill or cutter against hard material or drives a transducer which is coupled to liquids. This damping or cushioning effect tends to prevent hard metal-to-metal contact between the rotor and the housing which would cause damage to these components. The oil film is efficiently driven ahead of the moving bearing surface by means of an inwardly curved leading edge on the rotor. This turned-in leading edge facilitates the movement of the rotor up on to the oil film which then separates the rotor from the housing and forms an effective cushion or dampener therebetween.