Soon after 1802, Terry's production of wooden clocks grew considerably. Like other Connecticut clockmakers, Terry knew that apprentices could cheaply rough-cut wooden wheels for more skilled journeymen to shape precisely into clockworks, making clocks slightly more cheaply. And Terry was one of a number of Connecticut clockmakers who began to substitute water-powered machines for apprentices in the production of these rough-cut wheels. In 1802 or 1803, Terry purchased a mill to produce wooden clock wheels, which still had to be finished by hand by skilled journeymen clockmakers. He purchased a grain mill and used the water wheel and main shaft to run saws and lathes, which helped speed the production of parts. He later created jigs and fixtures to produce a large number of interchangeable clock parts. This allowed for the rapid adjustment and assembly of clocks, freeing Terry from the task of fitting and modifying each individual piece of each clock. Using his own ingenuity and inventiveness, Terry was thus able to speedily cut wheels, pinions, and other important clock parts accurately and repetitively.