Extruded Sheet Metal Hole

Extruded holes very close to the part edge can lead to sheet metal deformation or tearing.

Extruded sheet metal hole.

Extruded holes unipunch tooling can be used to simultaneously punch a hole and extrude the material down. Applications include for self tapping sheet metal screws or in thicker material to permit tapping for machine screws. 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.

Therefore the minimum distance between the extruded hole to edge if maintained. 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. For the tapped screw hole this is typically made using a male punch that creates the hole and extrudes the metal. Certain distance should be maintained between two extruded holes in sheet metal designs.

It is recommended that the minimum distance between two extruded holes should be six times the thickness of sheet metal. Creating an extruded hole using a punching process requires extreme pressure force.