Method of manufacturing rack guide base body in rack-and-pinion type steering apparatus and rack guide

A method of manufacturing a rack guide base body in a rack guide consisting of a rack guide base body for use in a rack-and-pinion type steering apparatus and a slider secured to said rack guide base body, comprising the steps of:

• forming in a die a cavity having a pair of semicylindrical convex surfaces each having at its one axial end a semicylindrical convex surface edge located on an inner side via a pair of inclined circular arc-shaped stepped portions each inclined with respect to an axial direction and extending in the shape of a circular arc and a perpendicular circular arc-shaped stepped portion perpendicular to the axial direction and extending in the shape of a circular arc in such a manner as to be connected at one end thereof to one end of one of the inclined circular arc-shaped stepped portions and to be connected at another end thereof to one end of the other one of the inclined circular arc-shaped stepped portions, said cavity further having a pair of flat surfaces each located between the pair of semicylindrical convex surfaces, a recessed surface located on one axial end portion side inwardly of the pair of semicylindrical convex surfaces and the flat surfaces, and a cylindrical surface located on another axial end portion side inwardly of the pair of semicylindrical convex surfaces and the flat surfaces;
• forming runner channels for respectively allowing said cavity to communicate with a gate at one of the flat surfaces and with an overflow well at the other one of the flat surfaces;
• die casting said rack guide base body by forcing molten metal of aluminum or zinc, or an aluminum alloy or a zinc alloy, from the gate into the cavity;
• and
• cutting off runners integrally joined to flat surfaces of said rack guide base body formed by the respective flat surfaces.