Pressure forming and piercing a hollow body

摘要

A shaped and pierced hollow workpiece is made by first confining a hollow metal blank in a cavity of a die which has an inner surface and is formed with a lateral compartment. The blank is internally pressurized to press it outward against the inner surface of the cavity while forming at the compartment an outwardly projecting bulge. A tool is pressed against an outer surface of the bulge and the bulge is pressed inward so as to at least partially to invert it and press a central portion of the bulge against an opposite inside wall of the blank. A hole is then machined through the blank where the central portion of the bulge engages the opposite inside wall.