When Cross joined the Cross Co. in 1933, the company was down to three people-his father, brother, and himself. The company had been a pioneering builder of engines and gears, but at that time the only profitable product was a gear-tooth rounding machine developed by the senior Milton Cross in 1912. Ralph Cross ceased all other operations and concentrated on the machine tool. As he concentrated on engineering, the company pioneered transfer machines, developing preset tools, tool control systems, sectionalized transfer lines, ballscrew feed units, and computerized machine tool systems.
Starting in 1960, he spent several years in Germany establishing engineering and manufacturing there. These were later expanded to Britain. Long a proponent of increased training of applications engineers, he headed the SME Engineering Education Foundation, and endowed a chair in manufacturing technology at MIT.