Abstract: A metal nut for clamping a metal or nonmetal x-ray target to a metal anode stem or a rotating anode x-ray tube. The nut body is basically circular and has an axial threaded hole. The body has an axially extending cylindrical portion that is contiguous with a generally convex portion on one side of the cylindrical portion and is concave on the other side. The concavity is surrounded by an annular land for transmitting compressive force to the target. A cross-section of the nut simulates a beam that is thickest axially adjacent the central threaded hole and decreases in thickness symmetrically radially away from the center so it will flex when tightened at room temperature and have residual force stored when hot to compensate the metals for thermal creep.