The NC positioning system converts the coordinate axis values in the NC part program into relative positions of the tool and work part during processing. Let us consider the simple positioning system shown in Figure 6.26. The system consists of a cutting tool and a worktable on which a word part is fixtured. The table is designed to move the part relative to the tool. The worktable moves linearly by means of a rotating leadscrew, which is driven by a stepping motor or servomotor. For simplicity we show only one axis in our sketch. To provide x-y capability, the system shown would be piggybacked on top of a second axis perpendicular to the first. The leadscrew has a certain pitch p (in/thread, mm/thread). Thus, the table moves a distance equal to the pitch for each revolution. The velocity of the worktable, which corresponds to the feed rate in a machining operation, is determined by the rotational speed of the leadscrew.