How CNC works

There is another article included in this web site called The Basics of CNC that explains how to program, setup, and operate CNC machines in greater detail. Additionally, we offer a series of products aimed at helping you learn how to use CNC machines. Here we're relating how CNC works in very general terms.
As you might already have guessed, everything that an operator would be required to do with conventional machine tools is programmable with CNC machines. Once the machine is setup and running, a CNC machine is quite simple to keep running. In fact CNC operators tend to get quite bored during lengthy production runs because there is so little to do. With some CNC machines, even the workpiece loading process has been automated. (We don't mean to over-simplify here. CNC operators are commonly required to do other things related to the CNC operation like measuring workpieces and making adjustments to keep the CNC machine running good workpieces.)
Let's look at some of the specific programmable functions.
Motion control
All CNC machine types share this commonality: They all have two or more programmable directions of motion called axes. An axis of motion can be linear (along a straight line) or rotary (along a circular path). One of the first specifications that implies a CNC machine's complexity is how many axes it has. Generally speaking, the more axes, the more complex the machine.
The axes of any CNC machine are required for the purpose of causing the motions needed for the manufacturing process. In the drilling example, these (3) axis would position the tool over the hole to be machined (in two axes) and machine the hole (with the third axis). Axes are named with letters. Common linear axis names are X, Y, and Z. Common rotary axis names are A, B, and C.