Abstract: An impact wrench for using fastening or unfastening fasteners comprises a cylindrical rotor coupled to a motor shaft, said cylindrical rotor including a projection on its inner surface, the projection having a circumferential width and an axial length; an anvil coupled to said cylindrical rotor, the anvil including a hammer member capable of rocking therein, the hammer member being engageable with said projection; a springloaded pusher for urging said hammer member towards said projection, wherein a spring support slides either on a deep cam face or a shallow cam face both produced on said inner surface of the cylindrical rotor, thereby allowing said spring to become compressed or relaxed against said hammer member.