Method of forming square holes in panels - involves passing expansible punch through previously drilled hole

摘要

To drill a hole with a polygonal contour in a panel having one of its side inaccessible, a circular orifice is first made and through it a punch with an expandable head is introduced. Before expansion, the square's side is smaller than hole's diameter. After, the cutting edges forming the shape of the final hole face the hidden side of the panel, against which they are pressed. Against the visible side, a matrix with a shape matching the punch's one is forced so the metal can be cut in the required shape.