Pratt was born in Woodstock Vt., served a seven-year apprenticeship, and then spent four years as a contractor at Gloucester Machine Works before moving to the Colt plant in Hartford, Conn. Two years later, he became superintendent of the Phoenix Iron Works in Hartford. He is generally credited with the design of the Lincoln miller (named for the owner of Phoenix) starting from an earlier miller designed by Lawrence. In 1860, Pratt and Amos Whitney, a contractor working for Phoenix, began moonlighting and received a contract for a thread-winding machine. This partnership grew into Pratt & Whitney, producing more than 7000 Lincoln millers over the next 40 years, as well as lathes, drilling machines, shapers, presses, drop hammers, and a variety of special machines. The firm became the leading exporter of machines and financed the development of the Rogers-Bond comparator and began to produce gauges. Pratt headed the firm until his retirement in 1898.