Abstract: A method for producing a worm shaft for use in a rotation control valve of a power steering mechanism. The worm shaft is formed with grooves which receive a control body and form therewith a fail safe structure. The grooves are formed evenly so that the permitted range of movement on either side of a neutral position is uniform. A cylindrical member is plastically deformed in two steps to form the outer side of the control valve. Then, while in a die having in inner shape corresponding to the desired outer shape of the worm shaft, a punch, having an outer shape corresponding to the desired shape of the grooves on the inner surface of the worm shaft and an enlarged-diameter portion, is pressed into a hole in the interior of one end of the member to thereby plastically deform the member to the desired final inner and outer configurations.