Method for plugging orifice

A method is disclosed for plugging/sealing an orifice/exit hole using a friction stir welding (FSW) process. Preferably a space inside the orifice remains. The method includes rotating a tool 1 that comprises a shoulder portion 2 having probe pin 3 attached at one end, such that the tool traverses the orifice of a member, thereby generating plastically flowing material of the member 200 that forms a plug portion 200c upon solidification, the plug portion plugging the orifice. The probe pin may have a cylindrical column configuration or may be a frustum of a right circular cone in order to reduce the load on the tool 1 during processing. The side surface of the probe pin is advantageously a smooth surface (i.e. no grooves), in order to control the flow of material into the orifice during welding and reduce defect formation. The disclosed method is particularly suited to plugging the ends of drilled channels formed in a member used for the manufacture of liquid cooling jackets and the like.