PB series is professional desiged ID mounted end prep equipment utilizes an expandable, self-centering mandrel system which mounts in the open end of a tube or pipe. Jaw blocks, corresponding to the size of pipe being worked on are placed on the mandrel. When a draw rod is tightened, jaw block bases are drawn up an inclined ramp, expanding the jaw blocks against the inside bore of the pipe. This provides a solid, torque-accepting grip for accurate machining operations.