B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
B21D9/00—Bending tubes using mandrels or the like
B21D9/01—Bending tubes using mandrels or the like the mandrel being flexible and engaging the entire tube length
B21D9/03—Bending tubes using mandrels or the like the mandrel being flexible and engaging the entire tube length and built-up from loose elements, e.g. series of balls