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Tube punching without mandrel

Punching process where a hole is punched in the workpiece without a mandrel.

Illustration of Tube punching without mandrel

The process

The workpiece is positioned below the punch which has a pointed tip. It is then pressed against the tube and thus creates a hole with the same diameter as the punch. As no die is used the surface around the hole is deformed, and the material is pushed aside by the punch, thus the hole folds inward. 

If dies are used, leave gap on the welded side to prevent weld cracks outside the hole.