Extruded Sheet Metal Hole

It is recommended that the minimum distance between two extruded holes should be six times the thickness of sheet metal.

Extruded sheet metal hole. An extruded hole is one that is generated at one station using a specially stepped punch that first shears a smaller hole and then follows through to deform the local area around the hole into a projection by limited forward extrusion. If extruded holes are too close it can lead to metal deformation. The following illustration shows the extruded hole geometry. You can imagine the shape as being a body to the punch of any shape and from this protrudes the punch pin of the diameter you want.

Certain distance should be maintained between two extruded holes in sheet metal designs. Creating an extruded hole using a punching process requires extreme pressure force. Extruded holes unipunch tooling can be used to simultaneously punch a hole and extrude the material down. Extruded holes very close to the part edge can lead to sheet metal deformation or tearing.

Applications include for self tapping sheet metal screws or in thicker material to permit tapping for machine screws. For the tapped screw hole this is typically made using a male punch that creates the hole and extrudes the metal.