Patent ID: 8256261

Claim:
A method of making inwardly collared through-passages in confronting legs of a sheet metal part of U-shaped cross section, said method comprising the steps of: positioning a first inner core in relation to a perforated sheet metal part between the legs of the sheet metal part in an area of holes; inserting a support bar through a first one of the holes into the sheet metal part for support of a backside of the first inner core; inserting into the first inner core a first shaping punch through a second one of the holes in opposition to the first hole, thereby forming an inwardly directed first collar, with the first inner core shaping an outside of the first collar and the first shaping punch forming an inside of the first collar; retracting the support bar and the first shaping punch; transferring the sheet metal part to replace the first inner core with a second inner core; inserting into the sheet metal part a centering bar through the collared second hole to center the sheet metal part in relation to the centering bar and to support a backside of the second inner core; and inserting into the second inner core a second shaping punch through the first hole, thereby forming an inwardly directed second collar, with the second inner core shaping an outside of the second collar and the second shaping punch forming an inside of the second collar.