METHOD AND APPARATUS FOR THE EXTRUSION OF BURRED EDGES OF HOLES IN A METAL SHEET, AS WELL AS A SHEET WITH ONE OR MORE EXTRUDED BURR HOLES FORMED IN ACCORDANCE WITH SAID METHOD

摘要

ABSTRACT:Method and apparatus for the extrusionof burr holes in a metal sheet, a punch with aconical end portion and adjoining cylindrical portionof a diameter which is greater than the liner burrdiameter being passed through the burr, the conicalend portion having a half apex angle between 10° and20°, and the axial length 1 of the cylindrical por-tion, the coefficient of friction m between said por-tion and the burr wall and the ratio of the burrwall thickness Sk before the operation and the burrwall thickness Sv after the operation being selectedso that: .