Five-Axis Machining Centers do not just move in the linear axes X, Y and Z. Instead, these machines also move in two rotary axes, often identified as A and B. The rotary axes tilt the tool with respect to the part. Physically, it can be either the tool that tilts or the part that tilts. Different machines accomplish the rotary motion in different ways. Some machines move the rotary axes only to position the tool or work outside of the cut. This is referred to as 3+2 machining. Moving the tool in this way dramatically increases the machining center’s access to features at different angles or on different faces of the part. A machine capable of 3+2 machining often can reach all of the machined features of the part in a single setup. True five-axis machining refers to the ability to not just position the tool along the rotary axes, but also to feed the tool through the cut using these axes. Interpolated combinations of A-axis, B-axis and linear axis motions can allow the tool to smoothly follow a contoured surface. This type of machining has long been important in the aerospace industry, where machined parts follow the aerodynamic forms of aircraft.