The pros must have a jig for hot twisting them to keep it uniform and concentric. A thick plate with a pin or bolt sticking out the correct diameter for the inner, open area, with 2 prong holes for the prongs to stick in, might work well for the initial twisting. Heat the prongs orange, stick the prongs into the prong holes in the plate beside the bolt, and twist the shaft while pushing down. Freehand the last twist later with another heat. Maybe?