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.

Extruded sheet metal hole.

For the tapped screw hole this is typically made using a male punch that creates the hole and extrudes the metal. 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. The following illustration shows the extruded hole geometry. It is recommended that the minimum distance between two extruded holes should be six times the thickness of sheet metal.

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. Extruded holes very close to the part edge can lead to sheet metal deformation or tearing. Therefore the minimum distance between the extruded hole to edge if maintained. Certain distance should be maintained between two extruded holes in sheet metal designs.

Applications include for self tapping sheet metal screws or in thicker material to permit tapping for machine screws. If extruded holes are too close it can lead to metal deformation.