Stepped punch

A punch for forming a punched opening in a metal sheet comprising:

• an elongated body having a first and a second spaced ends, said first end adapted to be held by a machine which, when activated, axially drives the body,
• said body having a punch section axially spaced from said second end of said body, said punch section terminating in an annular surface corresponding in shape and size to the punched opening, and
• an extension which extends axially outwardly from and is surrounded by said annular surface, said extension terminating at said second end of said body,
• wherein said extension has a length greater than a thickness of the metal sheet so that, as the punch is driven through the metal sheet, said extension forms a hole in the metal sheet smaller than the opening and thereafter said annular surface forms the opening in the metal sheet.