Interchangeable parts

Interchangeable parts are components of an assembly which are designed to meet specific tolerances so that any component of one type can be fitted with any component of a second type. This streamlines the manufacturing process, since all pieces are guaranteed to fit with all others, and it similarly creates the opportunity for replacement parts. The principle was originally put into practice in the manufacture of firearms during the 18th century by a number of inventors, including Honoré Blanc, Henry Maudslay, John Hall, and Simeon North.

Eli Whitney is often credited in this area but was never able to achieve the goal[1]. He gave a demonstration for Thomas Jefferson in 1798 and received a contract from the US Army in 1799

For centuries, guns and other devices were made one at a time by gunsmiths, and each gun was unique. If one single component of a weapon needed a replacement, the entire weapon either had to be sent back to an expert gunsmith to make custom repairs or discarded and replaced by another weapon.

The first concepts of interchangeability began to be developed in France during the 18th century, and around 1778, Honoré Blanc began producing some of the first firearms with interchangeable parts. Thomas Jefferson saw a demonstration in 1785, and five years later, Blanc demonstrates in front of a committee of scientists that his muskets could be assembled from parts selected at random. Jefferson took the idea back to the United States, where Eli Whitney and other inventors moved the concept forward.

Eli Whitney saw the potential benefit of developing "interchangeable parts" for the firearms of the United States military, and thus, around 1798, he built ten guns, all containing the same parts and mechanisms, and disassembled them before the United States Congress. He placed the parts in a large pile and, with help, reassembled all of the weapons right in front of Congress, much like Blanc had done some years before.

The Congress was immensely impressed and ordered a standard for all United States equipment. With interchangeable parts, the problems that had plagued the era of unique weapons and equipment passed, and if one mechanism in a weapon failed, a new piece could be ordered and the weapon would not have to be discarded. The principle of interchangeable parts also made mass production relatively easy. It was based on the use of templates, applied by semi-skilled labor using machine tools instead of the traditional hand tools.