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John T. Parsons pioneered numerical control for machine tools in the 1940s.
These developments were done in collaboration with his employee Frank L. Stulen, who Parsons hired when he was head of the Rotary Wing Branch of the Propeller Lab at Wright-Patterson Air Force Base, in April 1946. Together, they were the first to use computer methods to solve machining problems, more in particular, the accurate interpolation of the curves describing helicopter blades. In 1946, "computer" still meant a punched-card operated calculation machine. In 1948, Parsons' company, "Parsons Corporation" of Traverse City, Michigan, was awarded a contract to make the innovative and challenging tapered wings for military aircraft; they won the contract because they developed the computer support to do the difficult three-dimensional interpolation for the complex shapes, as well as the 800 steps long production cycle for the wing manufacturing. IBM was one of the subcontractors, as was MIT, which took care of the servomechanisms. The latter lab boosted the developments of CNC machining in the following decades, by developing reliable servo control in 1952 and the APT programming language for CNC machines. It was only after the servos were also steered by computers that real "numerical control" was realised. The initial developments of Parsons and Stulen were only about the calculations, and not the control: the results of the calculations were given to human operators that turned the wheels on the machine tool to generate the desired tool paths.
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