Method and apparatus of forming one-piece core cap stamping with keyway

A method of forming a core cap comprises the steps of selecting a blank of suitable sheet metal, forming a shallow U-shaped cup by stamping, drawing the cup in at least three successive stamping procedures to provide a deeper cup of smaller diametric dimensions having a bottom wall and a cylindrical wall, reverse stamping the bottom wall in order to form a reverse fold inwardly of the cylindrical wall with the bottom parallel and adjacent a plane containing the rim of the cup, causing a further step of drawing the bottom wall past the plane containing the rim of the cup such that an inner cylindrical wall is formed having an axial extent thereof which is greater than the axial extent of the outer cylindrical wall and forming a recess with a rear wall and side walls only in the inner cylindrical wall at the intersection with the reverse fold in at least three successive stamping steps such that the depth of the recess is gradually increased and the rear wall and side walls of the recess are formed with relative right angles with the minimum amount of internal stress in the wall material and the side walls are planar and symmetrically parallel to the axis of the inner cylinder, whereby the one-piece core cap has maximum strength characteristics and minimum internal wall stresses.