US Patent 7225541 Method for producing hollow rack bar

A method for forging a rack bar from a blank pipe. Prior to the rack forging process, a blank pipe is subjected to a process for obtaining an adjustment of a cross-sectional shape of the blank pipe. Such a preliminary adjustment is constructed by a swaging process for reducing an outer diameter of the blank pipe and a ironing process for obtaining a desired irregular cross-sectional shape of the blank pipe. The ironing process is such that locally thickened wall portions are obtained at length wise ends as well as tooth width ends of a rack forging die.