16 although other orientations of the cutting edge 16 can be utilized if desired the illustrated invention relies upom a pipe puller 14 to feed the pipe 10 horizontally across the vertically oriented cutting edge 16 the cutting edge 16 is formed on a knife member 26 having a first end 26a and a second end 26b which is carried by a frame 18 having a bore 20 therethrough the pipe 10 enters the bore 20 at an entrance end of the bore 20 in a direction illustrated by the arrow 22 the bore 20 is sized so as to closely receive the outside diameter of the pipe 10 a mandrel 24 is positioned within the bore 20 along the longitudinal axis of the bore 20 for centering and supporting the pipe 10 as its wall is severed while advancing through the bore 20 the mandrel 24 generally includes at least a portion which is cylindrical in shape and has a tapered end or leading edge 25 for inserting into the inner diameter of the pipe 10 preferably the mandrel 24 is made of mild grade steel as best illustrated in fig1 and 3 where like reference numerals are used for parts which appear in more than one figure the cylindrical shape of the mandrel 24 is modified to provide a portion having a flat surface 28 to aid in mounting the mandrel 24 within the bore 20 a support member 30 for the mandrel 24 is rigidly carried by the frame 18 and as illustrated the support member 30 is rigidly attached to the flat surface 28 by known methods such as welding as best illustrated in fig3 the cutting edge 16 of the knife 26 is positioned.