American system of manufacturing

The American system of manufacturing was a set of manufacturing methods that evolved in the 19th century.^[1] The two notable features were the extensive use of interchangeable parts and mechanization for production, which resulted in more efficient use of labor compared to hand methods. The system was also known as armory practice because it was first fully developed in armories, namely, the United States Armories at Springfield in Massachusetts and Harpers Ferry in Virginia (later West Virginia),^[2] inside contractors to supply the United States Armed Forces, and various private armories. The name "American system" came not from any aspect of the system that is unique to the American national character, but simply from the fact that for a time in the 19th century it was strongly associated with the American companies who first successfully implemented it, and how their methods contrasted (at that time) with those of British and continental European companies. In the 1850s, the "American system" was contrasted to the British factory system which had evolved over the previous century. Within a few decades, manufacturing technology had evolved further, and the ideas behind the "American" system were in use worldwide. Therefore, in manufacturing today, which is global in the scope of its methods, there is no longer any such distinction.

The American system involved semi-skilled labor using machine tools and jigs to make standardized, identical, interchangeable parts, manufactured to a tolerance, which could be assembled with a minimum of time and skill, requiring little to no fitting.

Since the parts are interchangeable, it was also possible to separate manufacture from assembly and repair—an example of the division of labor. This meant that all three functions could be carried out by semi-skilled labor: manufacture in smaller factories up the supply chain, assembly on an assembly line in a main factory, and repair in small specialized shops or in the field. The result is that more things could be made, more cheaply, and with higher quality, and those things also could be distributed further, and lasted longer, because repairs were also easier and cheaper. In the case of each function, the system of interchangeable parts typically involved substituting specialized machinery to replace hand tools.

Interchangeability of parts was finally achieved by combining a number of innovations and improvements in machining operations and machine tools, which were developed primarily for making textile machinery. These innovations included the invention of new machine tools and jigs (in both cases, for guiding the cutting tool), fixtures for holding the work in the proper position, and blocks and gauges to check the accuracy of the finished parts.^[2]