Parsons played the pivotal role in the development of numerical control. His company had made a number of manufacturing innovations in producing land mines, bombs, rockets, and helicopter rotor blades during World War 11. In 1947 he and Frank Stulen developed a method to produce contoured templets for checking blades by calculating successive machine positions on an IBM multiplier and then manually setting the positions on a boring mill. When Parsons learned that Lockheed was planning an aircraft with sculptured weight reduction pockets he convinced the Air Force by a series of demonstrations that this method could be adapted to a three-dimensional numerically controlled machine tool. He obtained a contract to develop such a machine with IBM to produce the data input device and Snyder to build the machine. Though MIT later took over the contract, his was the concept, the principles, and the persuasion that started numerical control of machine tools.