Method for producing burr-free blanks and the blanks produced thereby

Abstract

A method is provided for manufacturing a burr-free blank from an elongated sheet of flat metal stock comprising punching a first aperture in one surface of said metal stock, said first aperture extending only partially through said stock; simultaneously forming the lower burnished land portion of said blank; punching a second aperture in the opposite surface of said metal stock, coaxial with said first aperture, said second aperture extending only partially through said stock, said second aperture being smaller than said first aperture; simultaneously forming the upper burnished land portion of said blank, causing the material of said stock to fracture between said burnished land portions and recovering said burr-free blank. The resulting burr-free metal blank exhibits a shiny upper peripheral burnished land portion, a rough, fractured intermediate peripheral portion and a shiny lower peripheral burnished land portion, said lower land portion having a smaller circumference than said upper land portion.

Dependencies are inferred from the claim text.