CNC stands for "Computerized Numerical Control." It is a system that uses a computer to control the movements of a machine tool's cutting tools and spindle numerically, by program.
Instead of an operator turning handwheels, the machine cuts automatically, exactly as the program entered in advance instructs.
A Closer Look
CNC grew out of an earlier technology called NC (numerical control); adding a computer made far more advanced and flexible control possible.
Because virtually every numerically controlled machine tool sold today is a CNC machine, "NC" and "CNC" are often used to mean the same thing.
On a CNC automatic lathe, entering the shape and dimensions to be machined as a program lets the machine mass-produce identical parts to high precision while minimizing dimensional variation.
The ability to switch flexibly between many different parts simply by changing programs is one of CNC's greatest advantages.