The Keller Mechanical Engraving Co. was established in 1896 by Sidney A. Keller and Joseph F. Keller to make dies for manufacturing silverware. They had to import engraving and reducing machines from Europe, as the American machines then available were not sufficiently accurate. Joesph Keller, a mechanical engineer, eventually starting designing and building machines for their own use. Other companies expressed interest in purchasing Keller's machines, and in 1915 the first Keller E-1 Automatic Die Cutter Machine was sold to Crescent Tool Co. In 1916, the Keller brothers renamed their business to the Keller Mechanical Engineering Corp. (KME).
During World War I, KME made propellers. Meanwhile, Keller engineer John C. Shaw designed a new type of machine that used electrical controls to move a milling-machine head in response to a tracer following a pattern. The first Keller BG-1 tracer mill—a much larger machine than Keller's earlier models—was shipped to automobile parts maker Budd Co. in March 1921.
KME's timing was auspicious: the rapidly-growing automobile industry faced the challenge of converting a carved model of a car panel into a die for forming sheet metal. Keller's tracer mills were quickly adopted by the auto industry. These tracer mills were also used in making large molds, both for the auto industry and for manufacturing consumer goods. Keller was so strongly associated with this process that the pattern-following style of milling became known as "Kellering".
KME was acquired by Pratt & Whitney Co. in 1930. The Keller brand name lived on until at least 1960.