Abstract: A nut/clutch assembly for a rotary power screw, such as a linear actuator power screw, is disclosed in which the power screw is selectively rotated in one direction or the other, and in which the power screw has a pair of stops spaced apart from one another and which are rotatable with the power screw. A nut is provided having a central opening threadably engageable with the power screw, and the nut is threadably movable in axial direction along the power screw upon rotation of the latter. The nut has a circumferential groove thereon, and this groove has a base and a pair of spaced side walls. A collar is slidably received within the circumferential groove, and the collar is resiliently clamped onto the nut such that the collar frictionally engages the grooved base with a desired frictional force so as to permit the nut to rotate relative to the collar upon the nut being rotatably driven by the screw, and upon the collar being held in fixed rotary position.