Abstract: An apparatus (20) for counterboring a pipe (25) includes an expander unit (24), a shaft (26) extending from the expander unit, a flywheel (30) rotatably and slidably mounted on the shaft, a frame (34) mounted on the flywheel to be movable in a radial direction, a tool mount (50) and a guide wheel mount (52) formed on the frame, the tool mount traveling with the flywheel into the interior of the pipe during counterboring and the guide wheel mount traveling outside of the pipe during counterboring, the guide wheel mount being connected to the tool mount by guide wheel arm (51) having a radial member (54) that is axially offset to the rear of the tool mount by a distance at least the length of the counterbore to be machined in the pipe, a cutting tool (56) adjustably mounted to the tool mount, a guide wheel (72) rotatably mounted on the guide wheel mount, an inward force applying member (116) and an outward force applying member (122) connected between the flywheel and the frame such that the frame can be moved