Computer numerical control and second-operation
When World War II ended, the digital computer was poised to develop from a colossal laboratory curiosity into a practical technology that could begin to disseminate into business and industry. The advent of electronics-based automation in machine tools via numerical control (NC) and then computer numerical control (CNC) displaced to a large extent, but not at all completely, the previously existing manual and mechanically automated machines. Today, most CNC lathes have turrets, and so could logically be called "turret lathes", but the terminology is usually not used that way. Horizontal CNC lathes, with or without turrets, are generally called "CNC lathes" or "CNC turning centers" or "turning centers", and the term "turret lathe" by itself is still usually understood in context to refer to horizontal, manual turret lathes. The changed role in the production process that such machines now play is reflected in another name for them, second-operation lathe, as explained later.
The term "vertical turret lathe" (VTL) is applied to machines wherein the same essential design of the horizontal version is upended, which allows the headstock to sit on the floor and the faceplate to become a horizontal rotating table, analogous to a huge potter's wheel. This is useful for the handling of very large, heavy, short workpieces. Vertical lathes in general are also called "vertical boring mills" or often simply "boring mills"; therefore a vertical turret lathe is a vertical boring mill equipped with a turret. A CNC version is called a "CNC VTL".