a method and a device for welding plastic pipes made of thermoplastic material by a butt - welding method , wherein the pipes are held in a coaxial position in relation to one another by clamping points , are trimmed by a trimmer , which can be brought between the clamping points , and are heated up by heated tools , which can be fitted in place of the trimmer , wherein the heating of the free pipe ends to be welded has the effect of forming a melting region which forms a bead when pressing occurs , the pipe projection of the pipes being trimmed to a defined size .