What is CNC Machining?

Now, let’s quickly look at precision machine tools, how machining works, and what this has to do with part design. There isn’t space to cover the complete history of machine tools, nor to delve into saws, grinders, electrical discharge machining (EDM), and other ancillary equipment, but one key aspect any part designer should know is that most metal-cutting machines (they also cut plastic, by the way) can be roughly classified as either mill or lathe.

A great deal of technology lies behind each, but in a nutshell, a lathe grips a workpiece in a chuck and rotates it against a cutting tool, whereas a mill is the exact opposite, driving a rotating cutting tool against a workpiece that’s been clamped in a vise or fixture.

Despite their fundamental differences, CNC mills—more commonly known as machining centers—and CNC lathes (turning machines) share many similarities. All have multiple axis points of motion, with which to drive cutting tools around and through the workpiece, thus removing material. All use drills or end mills to make holes, but where lathes are equipped with groovers, threaders, and other turning tools, machining centers use face mills, slotting cutters, and other rotating tools.