· CNC Milling Toolpaths at a Glance. CNC milling toolpaths are typically egorized as 2D, 3D, 4axis, and 5axis. However, the term 2D is a bit misleading since this toolpath uses the Zaxis to position a tool for depth. For example, in the image below, we have a prismatic part whose features all reside at various heights on the XY plane.