mounting pin 42 through the end of the two ribs the pin 42 serves as a pivot or mounting post the pin 42 supports a link 44 which if permitted is free to rotate around the pin the link 44 is fairly wide so as to prevent twist or wobble its width coupled with the wide spacing of the splines 36 enables the link to rotate in a single plane and thereby correctly align a gripper means 48 the gripper means 48 has the form of an arcuate jaw which contacts the pipe it is sized to encompass about one third or one fourth of the exterior of the pipe the jaw mechanism includes a set of serrations 50 it will be appreciated that the serrations 50 are sloped to grip the pipe and take a bite into the metal to prevent skidding or sliding movement in other words the teeth 50 are cut so that they still bite into the pipe as the closure plate 16 is forced off of the end of the pipe 12 stated in another fashion the link 42 rotates from the angular position toward but does not achieve a more perpendicular position relative to the pipe to drive the teeth into the pipe the teeth are not bi directional that is they more readily skid in one direction than in.