that relatively unskilled workers could use sequentially to turn pinions , cut gears and produce sheet metal templates to ensure each internal part was the correct size . Using both specialized machines and a division of labor that had specific workers operating specific machines enabled Terry to produce many more clock parts than before . Moreover , those wheels , gears , pinions , arbors and plates were interchangeable enough for him to assemble a completed clock from a random selection of the required parts from any day ’ s production . By 1809 , Terry was able to increase his annual output to as many as 4,000 units , which he distributed to customers through a variety of Yankee peddlers .
In 1812 , Terry began using his techniques to build a clock movement that fit inside a wooden cabinet only 20 inches high . Throughout the next few decades , he and other clockmakers — many of whom had apprenticed under Terry — continued to use mechanization and the division of labor to produce parts for these smaller , less expensive and more easily marketable products . The internal parts were interchangeable not only with any one shop ’ s available inventory , but also with the parts made by other manufacturers . Using these techniques also enabled the clockmakers to lower their manufacturing costs and their retail prices . The shelf clock became one of the first domestically manufactured consumer products that was widely available to people of modest means .
By 1820 , factories in three Connecticut towns were producing more than 15,000 clocks per year . By 1836 , 16 factories in Bristol alone produced more than 100,000 finished clocks of assorted sizes and designs . And by 1850 , just two of the state ’ s largest factories produced more than 280,000 affordable clocks for customers in the United States and Europe .
Firearms
Creating firearms with interchangeable metal parts required much more precision than making the working parts of clocks out of wood or brass . To fit properly , clock parts needed to be accurate to within one-tenth of an inch . Parts of pistols or muskets needed to be accurate to within one-hundredth of an inch . So it came as no surprise that the path to making firearms with interchangeable parts was difficult and time consuming . That process
Courtesy of the Yale University Art Gallery
1822 portrait of inventor Eli Whitney by Samuel Finley Breese Morse , alongside Whitney ’ s sketch of proposed improvements to the musket lock , 1816 .
also required the innovations of more than a dozen gunsmiths and mechanics over several decades .
As Minister to France in the mid-1780s , Thomas Jefferson became aware of Frenchman Jean-Baptiste de Gribeauval ’ s system of using specialized lathes and jigs to manufacture standardized sizes of artillery pieces and shells . In a 1785 letter to Secretary of Foreign Affairs John Jay , he recognized the potential advantages of M . Honoré Blanc ’ s plan to use a similar system of dies , molds and jigs to produce muskets with interchangeable parts . The French Revolution interrupted Blanc ’ s efforts to convince French authorities to adopt his idea . A few years later , Jefferson asked Blanc to consider relocating to the United States . He was unsuccessful in that attempt and in his simultaneous effort to interest Secretary of War Henry Knox in Blanc ’ s system .
In 1798 , rumors of an impending war with France spurred the US Congress to authorize $ 800,000 to purchase new supplies of both cannons and small arms . Enter entrepreneur and inventor Eli Whitney . Apparently , he had heard or read of Blanc ’ s idea for manufacturing muskets with interchangeable parts . Without any relevant experience in arms making , Whitney had the audacity to suggest he could make 10,000 muskets with interchangeable parts over a two-year period . Secretary of the Treasury Oliver Woolcott , Jr . contracted with Whitney to achieve that goal — even though the purveyor of public supplies , Tench Coxe , doubted Whitney ’ s ability to perform .
During the next several years , Whitney struggled to deliver on this assignment , which he seemed to have had no basis for undertaking . He delivered 500 muskets in September 1801 and produced a total of 5,000 more by early 1809 ; none of them were made from interchangeable parts . Whitney appeared to be one of the earliest Americans to appreciate the concept of using specialized machinery to manufacture products with interchangeable parts . Indeed , throughout the next 150 years he was widely praised for that insight . Historians now know that he was more a promoter of that idea than an implementer of it .
At the signing of the Whitney contract , the federal armory at Springfield , Massachusetts was three years old ; it had only recently discovered how to use specialized machines to make a musket ( without interchangeable parts ) in nine days instead of 21 , and to increase its monthly production from 80 units to more than 440 . Another federal armory in Harper ’ s Ferry , Virginia was scheduled to begin production in 1801 . But given the urgent need for firearms , the government also contracted with private firearms makers . It authorized a producer of agricultural implements named Simeon North to make 500 horse pistols ; in 1800 , it granted him a contract to make 1,500 more . During the next 10 years , North stopped producing farm implements to concentrate on gun-making . He found that confining his workers to only one aspect of the manufacturing process both lowered his costs and increased the quality of the final product .
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