Which axis is typically controlled in the vertical movement of a CNC mill?

In a CNC mill, the Z axis is specifically responsible for controlling vertical movement. The Z axis defines the up and down motion of the cutting tool relative to the workpiece. This movement allows for precise depth adjustments during milling operations, such as drilling or contouring, where the tool must engage the material at varying depths.

In typical Cartesian coordinate systems used in CNC milling, the X and Y axes usually represent horizontal movements—X for left and right (side to side) and Y for forward and backward (in and out). The W axis is usually not applicable in standard CNC milling practices as it refers to additional axes that may be used in more advanced multi-axis machining processes. Therefore, when discussing vertical movement in CNC milling, the Z axis is the correct and relevant choice.