Abstract: A mandrel for producing connecting sockets at the end of thermoplastic pipes, the mandrel containing a first and a second row of retractable segments and apparatus for actuating these segments. The apparatus comprises a first and a second actuating bush arranged so as to move axially on a central shaft. The segments of the first and second rows of segments are pivotably mounted on bushes by means of parallel, axially displaced joints. Support surfaces, which are orthogonal to the mandrel axis, serve to hold the segments during their radial movement.