Definition
CNC (computer numerical control) machining is subtractive manufacturing where a computer program precisely controls the motion of a cutting tool relative to a workpiece, replacing manual control of the machine's axes. Milling, turning, EDM and grinding are all commonly performed on CNC equipment today.
Why 'CNC' alone doesn't determine cost
CNC machining is the umbrella category; the actual cost drivers, cycle time, tolerance and finish, come from the specific process (milling, turning, and so on), the machine's capability, and the program, not from "CNC" as a label by itself.
Where this comes up
Rarely stated directly; implied by the tolerances, finish and features a drawing specifies, which in turn imply what CNC process and machine can realistically produce them.
Common mistakes
Treating "CNC" as if it specifies a process on its own. CNC describes how a machine is controlled, not which process (milling, turning, EDM) is used or how capable a specific machine is.
CNC machining is the umbrella category; the actual cost drivers, cycle time, tolerance and finish, come from the specific process (milling, turning, and so on), the machine's capability, and the program, not from "CNC" as a label by itself.
See how Blake reviews a partFrequently asked questions
Is CNC a manufacturing process?
Not on its own; it's a control method used across several distinct processes such as milling, turning, EDM and grinding.
Is every modern machine tool CNC?
Most production machine tools today are CNC, though manual machines are still used for certain low-volume or specialized work.
Does CNC guarantee a certain tolerance or finish?
No, achievable tolerance and finish depend on the specific machine, process, tooling and program, not on CNC control by itself.