Forged axial collar around sheet metal plate hole - has increased wall thickness for thread cutting at inturned edge lip

摘要

The flat sheet metal plate (A) is drilled with a pilot hole (2) is subjected to a die forging process. During the forging stages, metal from around the edge of the pilot hole is displaced radially outwards such that a raised circular boss (4) is produced, projecting from one side of the plate only. A mandrel is then used to draw the raised edge of the hole in an axial direction in order to obtain a perpendicular collar (D) which is coaxial with the hole. Since the wall thickness of the collar has been increased by the forging operation, it is possible to cut an internal or external thread on it.