Abstract: An actuator includes a main shaft (16) at the input of a speed reducing gear unit (29-32) which carries an overtravel stop mechanism. The grounded stops (68) are adjustable by a worm gear (72) to allow a near infinite resolution of the position for the overtravel stop of the driven member (16). Rotating stop members (52) are mounted for translation along the main shaft (16). When traveling nut (44) engages a cam surface (60), cam follower (56) translates the normally rotating stop members (52) in a direction opposing the bias force of a compression spring (36) into a stop condition against the grounded fixed stop (68) on wheel (50).