Numerical Control

The concept of Numerical Control (NC) emerged in the post-World War II era as a solution to the challenge of manufacturing complex curved profiles for helicopter rotor blades and aircraft components. John T. Parsons, working for his family’s company, Parsons Corporation, conceived of using mathematical coordinate data to define the toolpath for a milling machine. The core idea was to feed the machine a series of discrete points defining a surface, and have the machine’s control system move the cutting tool between these points. This replaced the traditional, skill-intensive méthode of using physical templates (cams and tracers) or manual operation, which were slow and prone to error for complex shapes.

In 1949, Parsons partnered with the MIT Servomechanisms Laboratory, funded by the U.S. Air Force, to bring this concept to fruition. The project resulted in the first successful demonstration of an NC milling machine in 1952. This prototype used a vacuum tube-based controller that read instructions from a 1-inch wide, 7-track punched paper tape. The tape contained coded information for the desired positions of the machine’s three axes (X, Y, Z). Servomotors, receiving signals from the controller, would then drive the machine table and cutting head to the specified coordinates. The novelty was revolutionary: for the first time, a machine tool’s movements were governed not by a physical guide but by abstract, programmable data. This decoupled the part’s geometry from any physical master pattern, introducing unprecedented flexibility, repeatability, and accuracy into the manufacturing process. It laid the foundational groundwork for all subsequent automated machining.