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Interchangeable Parts

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Eli Whitney's Cotton Gin.

Until the early 19th century everything was hand made by a craftman. Every part was different even when serving the same function. You could not buy a new part. You had to go to a craftman and have it "tailor made" to replace the broken part. Needless to say such a process was time consuming and expensive, and sometimes impossible.

From Interchangeable Parts to Visual Basic, a Brief History, David Grimshaw, Ryerson University

But, for the first whole product whose parts could be interchanged, historian Ken Alder takes us to Paris in 1790 [1]. Gunsmith Honoré Blanc had made a thousand muskets and put all their parts in separate bins. He called together a group of academics, politicians, and military men. Then he assembled muskets from parts drawn at random from the bins. By then, Jefferson had already visited Blanc's workshop and written back to America about the method. . .

So what became of Blanc and his method? The answer's a surprise. For one thing, Blanc wasn't first to make muskets this way. Various French makers had worked on the idea since 1720. Furthermore, Blanc went into business and, by the time Whitney made his demonstration, was producing 10,000 muskets a year for Napoleon.
Then, in 1806, the French government sacked the whole process. Why? By using unskilled labor, Blanc's method had made manufacturers independent of government control over the old crafts. The government raised the arcane argument that workers who don't function as a whole can't produce harmonious products. They simply declared that Blanc's method wasn't working and they scrapped it.

Lienhard, John H., No. 1252 Interchangeable Parts, in The Engines of Our Ingenuity, M.D. Anderson Professor Emeritus of Mechanical Engineering and History at the University of Houston.

Edinburgh Encyclopedia, 1832.

But the first country that tried to manufacture parts that could be interchanged in factory assembly was France. In 1785 Benjamin Franklin told about a French gunsmith who'd managed to make muskets with interchangeable parts. Still, when Eli Whitney got American government support to do the same thing in 1794, he did it by convincing people the idea was unknown in Europe. Worse than that, he also did some hand-work and hand-selection on the parts he used in his demonstration.

Making guns with truly interchangeable parts was very hard to do. We'd made clocks with interchangeable parts as early as 1828 — that was easier. But the military wanted to be able to interchange the parts of guns in the field. They never did manage to do that with their service revolvers, but their muskets and rifles could be made with looser tolerances. By 1860, on the eve of the Civil War, we'd achieved interchangeability in military rifles and muskets, but we were far from it in making handguns.

Lienhard, John H., No. 101 Interchangeability, in The Engines of Our Ingenuity, M.D. Anderson Professor Emeritus of Mechanical Engineering and History at the University of Houston.

Van Slyke, Eli Whitney Armory Site , c. 1879. Source: Eli Whitney Museum

While Eli Whitney is best remembered as the inventor of the cotton gin, it is often forgotten that he was also the father of the mass production method. In 1798 he figured out how to manufacture muskets by machine so that the parts were interchangeable. It was as a manufacturer of muskets that Whitney finally became rich. If his genius led King Cotton to triumph in the South, it also created the technology with which the North won the Civil War.

The Cotton Gin, The Eli Whitney Museum

Whitney refined and successfully applied his revolutionary, "Uniformity System" of manufacturing interchangeable components. Faced with skepticism and delays in implementing his new production method, Whitney convinced President John Adams of the great significance of his innovative approach by demonstrating that randomly selected parts could be fitted together into a complete, working musket lock. Though it took ten years to deliver the last of the muskets, the federal government's investment and support enabled Whitney to prove the feasibility of his system and establish it as the leading source of the modern assembly line. He demonstrated that machine tools--manned by workers who did not need the highly specialized skills of gunsmiths--could produce standardized parts to exact specifications, and that any part could be used as a component of any musket. The firearms factory he built in New Haven, Conn., was thus one of the first to use mass production methods.

From Interchangeable Parts to Visual Basic, a Brief History, David Grimshaw, Ryerson University

Jefferson was president when Eli Whitney duplicated Blanc's [gunsmith Honoré Blanc in 1790] demonstration 18 years later. No one realized it then, but Whitney was faking it. He'd carefully hand-crafted each part so they'd fit together. Whitney sold the government a huge contract for four thousand muskets. He took eight years to deliver them and then the parts weren't interchangeable after all.

But other Americans went on to make the method work. Before the Civil War, we had rifles with parts that could be swapped. After the war, we began making complex merchandise like sewing machines and typewriters with interchangeable parts.

No. 1252: Interchangable Parts, Engines of Our Ingenuity

Whitney designed a new gun and the machinery to make it. His machine manufactured parts exactly alike. Each part would fit any of the guns he made. Whitney also created division of labour, in which each person specialized in making one part of the gun. The final step was merely to assemble the interchangeable parts.

Eli  Whitney, Ferdinando Family History

Remington, model No.2, introduced 1878. E. Remington & Son, a firearms maker founded in 1816, made occasional forays such as making sewing machines and farm implements. Source: MyTypewriter.

Ford Motor Company, Detroit, Michigan. Source: Library of Congress

After the Civil War, the idea of interchangeable assembly spread quickly through American manufacturing. The small-arms maker Remington expanded the idea — first to make sewing machines and then typewriters. By the time Henry Ford carried the assembly line to such a remarkable level in 1913, America was already established as the world leader in production.

Lienhard, John H., No. 101 Interchangeability, in The Engines of Our Ingenuity, M.D. Anderson Professor Emeritus of Mechanical Engineering and History at the University of Houston.

Additional Resources

Hounshell. D. A., From the American System to Mass Production, 1800-1822: The Development of Manufacturing Technology in the United States. Baltimore: Johns Hopkins University Press, 1984.

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