The development of numerical control was the next major leap in the history of automatic lathes—and it is also what changed the paradigm of what the "manual versus automatic" distinction meant. Beginning in the s, NC lathes began to replace manual lathes and cam-op screw machines, although the displacement of the older technology by CNC has been a long, gradual arc that even today is not a total eclipse. By the s, true CNC screw machines (as opposed to simpler CNC lathes), Swiss-style and non-Swiss, had begun to make serious inroads into the realm of cam-op screw machines. Similarly, CNC chuckers were developed, eventually evolving even into CNC

The machine is controlled electronically via a computer menu style interface, the program may be modified and displayed at the machine, along with a simulated view of the process. The setter/operator needs a high level of skill to perform the process. However, the knowledge base is broader compared to the older production machines where intimate knowledge of each machine was considered essential. These machines are often set and operated by the same person, where the operator will supervise a small number of machines (cell).

In the hierarchy of manufacturing machines, the screw machine sits at the top when large product volumes are needed. An engine lathe sits at the bottom, taking the least time to set up but the most skilled labor and time to actually produce a part. A turret lathe has traditionally been one step above an engine lathe, needing greater set-up time but being able to produce a higher volume of product and usually requiring a lower-skilled operator once the set-up process is complete. Screw machines may require an extensive set-up, but once they are running, a single operator can monitor the operation of several machines.

Most CNC Swiss-style lathes today use one or two main spindles plus one or two back spindles (secondary spindles). The main spindle is used with the guide bushing for the main machining operations. The secondary spindle is located behind the part, aligned on the Z axis. In simple operation it picks up the part as it is cut off, and accepts it for second operations, then ejects it into a bin, eliminating the need to have an operator manually change each part, as is often the case with standard CNC turning centers. This makes them very efficient, as these machines are capable of fast cycle times, producing simple parts in one cycle (i.e., no need for a second machine to finish the part with second operations), in as little as – seconds. This makes them ideal for large production runs of small-diameter parts.

In a single-spindle machine, these four operations would most likely be performed sequentially, with four cross-slides each coming into position in turn to perform their operation. In a multi-spindle machine, each station corresponds to a stage in the production sequence through which each piece is then cycled, all operations occurring simultaneously, but on different pieces of work, in the manner of an