Abstract: A portable pipe cutter is provided having a rotating annular cutter with radially advancing blades which are driven as they are rotating around a stationary helically threaded plate. Small keys attached to each of the blades each have a threaded face which engages the helically threaded advance plate so that as the cutter member rotates, the inwardly directed blades not only rotate around a pipe but also advance linearly as a function of angular distance traverse. The unit is characterized by being portable, and having the rotating cutter member separable into semi-annuli, as is the bearing ring in which the cutter member rotates, so that the entire structure can be used anywhere along a continuous pipe, without being inserted over the end.