Interchangeable Standardized Parts: the “American Manufacturing Method”

Standardized parts allow parts of a machine to be swapped out, enabling factories to manufacture parts without worrying about the larger machine. Interchangeable parts vastly lowered manufacturing costs.

Check out the video we created about interchangeable standardized parts:

Today, everything from cars to computers, software and even food, is interchangeable. We’re annoyed that a USB plug only works in one direction but the idea that such a plug works at all — that it fits into countless computers and makes enormous data stores accessible — is a big yawn.

Today, we take it for granted that parts can be replaced and that every part is the same. But, at the time, this was an enormous breakthrough.

Le Blanc

Messrs. Le Blanc is a Frenchman gunsmith who devised a musket with interchangeable parts and the idea in general. Gaspard Cotty describes the innovation in a multi-page footnote in his 1806 book, Memoire sur la Fabrication des armes portatives de guerre.

On a table is place a collection of random parts to create about 50 muskets. An observer picks random pieces then fits them together into a fully functioning musket. Muskets were individually handcrafted, at enormous cost, before Le Blanc’s innovation.

Interchangeable parts vastly lowering the cost of maintaining an army.

Then US Ambassador to France Thomas Jefferson witnessed Le Blanc’s demonstration and invited him to bring it to the US. Le Blanc declined, wishing to remain in France. France, concerned about job loss, declined to embrace Le Blanc’s method.

There is some speculation that the idea of standardized parts predates Le Blanc, though Cotty’s 1806 book — written in a pre-Napoleanic french dialect — shows that to be unlikely.

Specifically, Cotty notes that Le Blanc:

  • Is the first to use “hardened steel” (a process apparently in use for some time in the steel industry) to produce the lock of a firearm; Le Blanc created this technique in 1777.
  • Highlights the pros and cons of interchangeable standardized parts for muskets.
  • Specifically details Le Blank presenting 50 or 60 rifles to Mr. de Gribeauval, “inspecteur general de l’artillerie,” the inspector general of the French artillery, in 1789 before the French Revolution.
  • Le Blanc then had his men take the rifles apart, mix up the parts, and put them back together. However, there were enough defects that de Gribeauval decided to rely on “old” (their word) manufacturing methods.
  • de Gribeauval was also concerned with complaints from soldiers about the standardized parts muskets and with the effect on jobs.

There was some speculation that Jefferson’s recounting of the French demonstration was an urban legend. Jefferson mentions the demonstration in a 1789 letter to Henry Knox but there is no other mention despite the enormity of the innovation. However, Cotty’s account makes the idea that Jefferson fabricated the idea to gain traction extremely unlikely.

Eli Whitney

Jefferson eventually returned to the US and brought the idea of standardized parts to Eli Whitney, inventor of the cotton gin. Jefferson, in his earlier role as Secretary of State, failed to process Whitney’s cotton gin patent in a timely manner. In all fairness, Jefferson openly did not like patents and was slow to process virtually all patent applications, not just Whitney’s. For example, he eventually granted four separate people a shared patent for the steamboat despite that two of the applicants didn’t have working boats. Jefferson was openly hostile to patents.

Due in part to the lack of patent protection knockoff cotton gin’s thrived and Whitney made no profit. Feeling a sense of guilt, Jefferson brought Whitney the idea for a musket based on interchangeable parts.

Jefferson worked with Whitney to repeat the same demonstration as Le Blanc, mixing up a bunch of parts then assembling a musket. However, Whitney’s parts all fit together perfectly, probably because historians agree they cheated and marked parts Whitney knew were pre-fitted.

Whitney, with his well-known name and Jefferson’s help, secured a contract to build an interchangeable part musket. His factory never quite worked — he could not build the parts to tight enough tolerances — but his children, who took over the factory, eventually succeeded.

Despite that Le Blanc of France created the concept, interchangeable standardized parts became known as the American Manufacturing Method.


Later, Sam Colt thrived on interchangeable parts. Ford was also an interchangeable parts fanatic, to the point he insisted that shipping crates use the same size planks for reusability.

2 thoughts on “Interchangeable Standardized Parts: the “American Manufacturing Method””

Leave a Reply

Your email address will not be published. Required fields are marked *