Apparatus for continuous extrusion of an aluminum sheathing on to a core cable includes a rotatable wheel formed with two identical circumferential grooves outwardly bounded by arcuate tooling discharging through radial exit apertures to an extrusion chamber positioned around a portal mandrel. A powered pay-off reel is arranged continuously to supply core cable through the mandrel while aluminum sheathing is extruded as a loose fit from extrusion chamber around the core cable. The extruded cable is discharged through cooling device to roller corrugator including a rotating frame mounted on carriage freely moveable axially of the cable and provided with a rotational drive having a roller arranged to form a continuous helical indentation in the sheathing. Pneumatic actuating cylinders positioned on the carriage provide a constant, low magnitude, tension on the portion of the sheath intermediate the extrusion chamber and roller corrugator and limit forces tending to distort the uncooled sheath.