User:Three-quarter-ten/Turning center

A turning center is a machine tool with computer numerical control whose basic form factor shows lathe ancestry, meaning that the workpiece is mounted to the main spindle and is rapidly rotating for many of the cuts. CNC lathes were the original type of turning center. They began as conventional metalworking lathes retrofitted with CNC control. Their tooling was all of the non-live type, meaning that tool bits, drill bits, endmills, and so forth were used without rotating (with their motion relative to the workpiece being provided by the workpiece's own rotation). Such lathes were first built in the 1950s immediately after the invention of numerical control. By the 1970s they were fairly widely disseminated throughout medium-sized and large enterprises in the machining industries. During the 1980s their dissemination reached widely into small businesses as well.

In the 1990s, live tooling (tooling with secondary rotary axes in addition to the main spindle axis) and back spindles (a "second main spindle axis" at the tailstock end) began to see wider use. The first advantage of live tooling was the ability to perform light milling on a workpiece during the same setup as the turning work. The advantage of the back spindle was the ability to make cuts on the back side of a part without the job routing and setup work that would be associated with moving the part to another machine. Both of these developments decreased the incidence of second, third, and fourth operations that required a move to another machine (with its attendant routing and setup overhead). This brought many kinds of parts to completion much more efficiently than had been done in the past, and usually with a higher degree of automation.

In the 2000s, CNC lathes with live tooling evolved into machine tools that were such thorough hybrids of lathes and mills that a new class of machine, the turn-mill or mill-turn, was born, just as [mechanically automated] multispindle automatic lathes were evolving into rotary transfer machines.