Low-cost high-density gang punch

A gang-punch apparatus for punching selected hole patterns in thin sheet material comprises:

• a lower stripper plate having a top surface and a bottom surface formed with a plurality of vertical through-holes;
• a guide plate formed with a plurality of corresponding vertical through-holes and having a top surface and a bottom surface;
• a pressure chamber or other expandable/contracting means between the guide plate and lower stripper plate, the plates when the chamber is not compressed being in an extended non-punching position and, when compressed, the plates being in a contracted punching position;
• a plurality of elongated punch pins having an upper end and a lower end and which are axially slideably disposed in the vertical through-holes of the guide and stripper plates with the upper ends of the pins being larger so that the upper ends of the pins rest on the top surface of the guide plate, the pins being either non-punching punch pins or punching punch pins and being of a length when the guide and stripper plates are in a contracted punching position, the lower ends of the punching punch pins extend below the bottom surface of the stripper plate and through a thin sheet material on which the stripper plate rests and a die;
• a program plate having a top surface and a bottom surface disposed on the top surface of the guide plate, the program plate formed with a plurality of vertical through-holes overlying non-punching punch pins;
• a clearance plate disposed on the top surface of the program plate and formed with a plurality of vertical through-holes corresponding to the vertical through-holes of the guide and stripper plates, the clearance plate being of a thickness to contain in the clearance plate through-holes the non-punching punch pins when the guide and stripper plates are in a contracted punching position;
• and
• means to exert a force on the clearance plate to force the guide and stripper plates closer together thereby extending the lower ends of the punching punch pins below the bottom surface of the stripper plate and forming a hole pattern in the thin sheet material which is in contact with the surface of the stripper plate with the non-punching punch pins extending into the vertical through-holes of the clearance plate so that there is no punching of the thin sheet material at the non-punching punch pin locations.