Turning is machining in which the material (workpiece) is rotated and a fixed cutting tool is brought against it to remove material.
Because the tool works on rotating material, turning excels at producing shapes with round cross-sections — cylinders, cones, and threads.
It is the core operation performed by lathes and CNC automatic lathes.
A Closer Look
Turning encompasses many operations: "OD turning" of the outer surface, "facing" to flatten end faces, "boring" to open up the inside, "threading" to form threads, "grooving," and "parting" to separate the part from the bar.
Finishing a single part typically involves several of these in succession.
It is the counterpart of milling, in which the tool rotates; an easy way to remember the difference is "turning rotates the material, milling rotates the tool."
A CNC automatic lathe centers on turning but combines it with milling and drilling by rotating tools to finish complex parts.