Abstract: A support arm assembly for a pipe bending machine, including one or more linear ledges arranged along the arm; a mandrel including a piece for intercepting the ledges through a click (106) switching between a raised rest position and a lowered working position by the displacement of an eyelet, in which it can slide, having raising edges (105) against which click (106) is loaded, under the actuation of an air cylinder, under the control of means that also control the opening/closing of the pipe carrier gripper (16) of the mandrel; and angular ledge dowels with a sense cut (200) being provided on the periphery of the mandrel, cooperating with a spring-loaded locator.