Hydraulic piston made from rolled sheet metal, method for its manufacture and intermediate product of the method

Method of manufacturing a hydraulic piston comprising the steps:

• punching a disk-shaped round blank out of a piece of rolled sheet metal;
• deep-drawing the disk-shaped round blank into a cup shape by means of a bottom die and a punch;
• stamping the cup-shaped blank to form a piston head and a cylindrical outer surface of the hydraulic piston;
• and
• incorporating an annular groove into an outer surface of the hydraulic piston;
• whereby said stamping step forms a portion of an inner surface of a side wall of the hydraulic piston adjoining an open end thereof and extending in axial direction over the annular groove to have a cylindrical shape, and whereby a said deep-drawing step forms the side wall to have a thickness that decreases monotonically from the portion of the inner surface up to the piston head.