Deforming double-walled bodies

Full Title

Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces (stamping using resilient pads B21D22/10) > by applying fluid pressure > Deforming tubular bodies (corrugating tubes by applying fluid pressure B21D15/03, B21D15/10) > Deforming double-walled bodies