US Patent 7836580 Transformer winding and production method thereof

A method for producing a winding, particularly for electrical transformer from a cylindrical tubular metal element of polygonal cross-section, includes steps of machining, in a first series of passes, a first series of cuts substantially parallel to one another through all of the sides of the tubular element with the exception of a last one of said sides, and machining, in a second series of passes, a second series of cuts in said last one of said sides in order to ensure that junctions of the first series of cuts open out in the sides adjacent to the second series of cuts, so that the first and second series of cuts are continuous with respect to one another and constitute a single groove of helicoidal shape.