Patent ID: 11931790
Assignee: nan
Field: Machine tools (Mechanical engineering)
Classification: CPC B  Y | IPC B

Claim 0:
1. A method of punching a rectangular hole through a selected side wall of multiple side walls of a longitudinally extended rectangularly shaped tubular workpiece, comprising:
providing a mandrel that extends in a longitudinal direction, said mandrel carrying a two-sided die thereon, said two sided die having a die opening, and wherein the workpiece is removably sleeved over said mandrel;
providing a rectangular punch aligned with the selected side wall of the workpiece and having a cutting end disposed in correspondence with and received by said die opening of said two-sided die subsequent to being displaced in a direction to pass through the selected side wall of the workpiece, said direction defining a punching direction and said punch having a dimension in a direction transverse with respect to both the punching direction and the longitudinal direction, the dimension of the punch in the transverse direction being limited only by an internal dimension of the workpiece in the transverse direction between side walls of the workpiece adjacent the selected side wall;
applying a compressive force by a piston rod in the transverse direction to respective portions of the multiple side walls of the workpiece adjacent the selected side wall of the workpiece in correspondence with said die opening of said two-sided die, said compressive force being of a magnitude to elastically deform the workpiece in the transverse direction in a range of 0.015-0.020 inches and thereby support the multiple side walls of the workpiece against deformation thereof during punching of the rectangular hole;
reciprocatingly displacing said rectangular punch through the selected side wall of the workpiece to form the rectangular hole therethrough; and
removing the workpiece from said mandrel.