Patent ID: 6109086
Filing Date: 2000-08-29
Classification: B21D

Abstract:
A punch for forming a slugless hole in sheet material and forming a conical extrusion around the hole comprising:an elongated cylindrical shank having a hole-forming portion at one end thereof,said hole-forming portion including an extruding portion axially outwardly of the end of said shank and a cylindrical piercing tip, of smaller diameter than said extruding portion, axially outwardly of said extruding portion,said shank, extruding portion and piercing tip having a common longitudinal central axis,said piercing tip having an outer end formed with a flat radial surface perpendicular to said central axis and a flat ramped surface extending at an acute angle to said radial surface,said piercing tip being adapted, upon initial axially outward advance of said shank, to punch a hole in the sheet material leaving punched-out material attached to an edge of the hole,said extruding portion being adapted, upon further axially outward advance of said shank, to form in the sheet material a conical extrusion around the hole.