The tubes with radially welded on oval or rectangular cross section pegs are made by using hollow spot welding electrodes into which the pegs are fitted prior to fixing. For fixing two electrodes are disposed on radially opposite sides of the tube engaging it simultaneously for the welding operation. The electrodes have pref. cross shaped cross section bores able to accept the pegs in two alternative positions with the longer cross sectional axis displaced by 90 degrees.
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