Extruded Sheet Metal Hole

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

Extruded sheet metal hole.

Creating an extruded hole using a punching process requires extreme pressure force. 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. 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.

Alternately the hole could be pre pierced in a separate station and then the edges extruded at a second station. Tap fix screws for extruded holes in light gauge steel this article provides tap fix hole size recommendations for metals using light gauge punched extruded materials. Therefore the minimum distance between the extruded hole to edge if maintained. If extruded holes are too close it can lead to metal deformation.

The following illustration shows the extruded hole geometry. Extruded holes unipunch tooling can be used to simultaneously punch a hole and extrude the material down.