In Adam Smith's pin factory one man draws out the wire, another straightens it, a third cuts it, a fourth points it, and a fifth grinds the top for the head. Making a pin was divided into about eighteen distinct operations, some of them done by separate workers. Smith also worried about the division of labor. He wrote that it could make a worker as stupid and ignorant as it is possible for a human creature to become, unless government took steps against it. Interchangeable parts are old. Evidence of them goes back over two thousand years to Carthage in the First Punic War, where ships had standardized parts marked with assembly instructions. In the late 1700s French General Gribeauval promoted standardized weapons, issued as a royal order in 1765.
Around 1778 Honoré Blanc in France made some of the first firearms with interchangeable flintlock mechanisms. He showed a committee that locks picked at random from a pile of parts would fit his muskets, and Thomas Jefferson saw his work in 1785. In 1798, with President George Washington's approval, Eli Whitney signed a contract to mass-produce 12,000 muskets built under the new system of interchangeable parts. In Britain, gunsmith Henry Nock delivered 12,010 locks to the Board of Ordnance between 1793 and 1795 that were meant to be interchangeable. Simeon North and John Hall, working before 1832, were able to mass-produce guns with moving parts by milling rough-forged parts to near size and then filing them to gauges by hand with filing jigs.
Interchangeable parts mean that a broken part can be replaced with a new one instead of making a new part by hand to fit. That solved the difficulty of repairing old equipment. Modern mass production was only possible after machine tools and techniques to make such parts were developed in the mid-19th century. Mass production means making many copies of products, very quickly, using assembly line techniques where each worker does one step rather than a whole product. The term was popularized by a 1926 Encyclopaedia Britannica supplement article based on correspondence with Ford Motor Company. Ford management ran time studies and experiments to mechanize its factory processes, focusing on minimizing worker movements. While Taylor focused mostly on the efficiency of the worker, Ford also substituted machines for labor, thoughtfully arranged, wherever possible.
Frederick Winslow Taylor began developing scientific management, also called Taylorism, in the United States in the 1880s and 1890s in manufacturing, especially steel. Its peak of influence came in the 1910s. The ideas stayed influential into the 1920s. Henry Ford wrote down the principles of assembly. Place tools and workers in the order of the operations. Then each part travels the least possible distance. Use work slides or carriers. A worker who finishes an operation drops the part always in the same, most convenient place. Gravity carries it to the next worker if possible. Designing an assembly line is a math puzzle called line balancing. Tasks must follow an order. So there is no screw before the hole is drilled. The total task time at each station must fit within a cycle time before the product moves on.
In early 1913 Ford tried a moving line for flywheel magnetos. The work was divided into 29 operations done by 29 men along a moving belt. Average assembly time dropped from 20 minutes to 13 and then to five. The first moving chassis line dragged the chassis across the floor with a rope and windlass. Production time fell from about 12 hours to just under six. Although Henry Ford is remembered for saying customers could have any color so long as it was black, the Model T was not available in black in its first years. From 1908 to 1913 it came only in gray, green, blue and red. The all-black policy was finally put in place in 1914.
Words to know
- interchangeable: swappable
- muskets: old guns
- windlass: rope winch
- balancing: evening out
