Abstract: The present invention is directed to a knife assembly which is used to cut a rotating tube, such as a paper or plastic tube. The circular knife remains stationary during the cutting. After a number of cuts, the knife becomes dull. The present knife assembly rotates the circular blade or knife through a predetermined angle which results in an incremental movement of the circumference or cutting edge of the knife. A shaft has a first end which mounts the circular knife and a second end connected to a one-way clutch. An arm extends from the one-way clutch. Movement of the arm in a first direction rotates the shaft and moves the cutting surface of the knife. The arm is returned in an opposite direction. During this return arm movement the shaft and knife remain stationary. The assembly is then ready for the next cycle.