Abstract: Rotary actuator mechanism in which relative axial movement of two magnetizable members is converted into relative rotative movement. Each magnetizable member has a plurality of inclined engagement surfaces, the inclined engagement surfaces of one magnetizable member are in an adjacent opposed position with respect to the inclined engagement surfaces of the other magnetizable member. Electromagnetic means are employed to provide the relative axial movement. An annular member retains a plurality of ball elements which are adapted to roll on opposed inclined surfaces. Relative rotative movement between the magnetizable members is created by action of the ball elements and the inclined engagement surfaces, with relative axial movement between the magnetizable members.The degree of relative rotative movement of the actuator mechanism is adjustable by adjustably limiting the relative axial movement between the two members. The magnetizable members are arranged to provide maximum magnetic operating efficiency.