Extruded Sheet Metal Hole

Design for manufacturability sheet metal guidelines bends for the ease of manufacturing multiple bends on the same plane should occur in the same direction.

Extruded sheet metal hole.

It is recommended that the minimum distance between two extruded holes should be six times the thickness of sheet metal. In low carbon steel sheet metal the minimum radius of a bend should be one half the material thickness or 0 80 mm. 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.

This procedure creates in effect the. 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. Extrusions our commonly used to accept sheet metal screws or permit tapping into a deeper distance than just the material thickness. It is always better to specify hole diameters that are greater than the sheet s thickness t.

A pre punched hole is required as a one hit pierce and extrude gives poor hole quality and has limited adjustment on the machine. The following illustration shows the extruded hole geometry. Minimum hole diameter the diameter of the hole in sheet metal part should not be very small small holes are created by piercing operation and for manufacture small holes small sizes punches are required. Applications include for self tapping sheet metal screws or in thicker material to permit tapping for machine screws.

Die buttons with oversized internal diameters typically with a 020 radius instead of a cutting edge are used to permit the material to flow downward and punch an extruded hole. Alternately the hole could be pre pierced in a separate station and then the edges extruded at a second station. In a sheet metal design specifying hole sizes locations and their alignment is critical. Creating an extruded hole using a punching process requires extreme pressure force.

Avoid large sheet metal parts with small bent flanges. 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.