Mass production is notable because it permits very high rates of production per person and therefore provides very inexpensive products.
The economies of mass production come from several sources. The primary cause is a reduction of nonproductive effort of all types. In craft production, the craftsman must bustle about a shop, getting parts and assembling them. He must locate and use many tools many times, perhaps hundreds of times to assemble a complex product such as a clock.
In mass production, each worker repeats one or a few related tasks that use the same tool to perform identical or almost identical operations on a stream of products. The exact tool and parts are always at hand. The worker spends no time going and getting them.
Mass production systems are usually organized in assembly lines. The assemblies pass by on a conveyor, or if they are heavy, hung from an overhead monorail.
In a factory for a complex product, rather than one assembly line, there may be many auxiliary assembly lines feeding sub-assemblies (i.e. car engines or seats) to a backbone "main" assembly line. A diagram of a typical mass-production factory looks more like the skeleton of a fish than a single line.
Another important economy is that the factory can purchase very large amounts of materials. This reduces the overhead costs (shipping, purchasing negotiations, paperwork, etc.) associated with purchasing the parts.
A final very important strategy is vertical integration. In this strategy, the manufacturer produces all or most of the parts and subassemblies that go into the product. For example, at one point, Ford Motor Company literally mined iron ore in Minnesota and turned it into cars in Detroit, capturing all the profits from all the processes that added value to iron ore.
Nowadays, rather than assembling everything, factory managers choose which assemblies to produce based on the return on investment (ROI) that each assembly process can produce. The basic plan is to out-source unprofitable subassemblies to other organizations. Often, such organizations can afford specialized equipment or organization that makes them substantially more efficient than an ordinary factory at a particular task.
While Ford was first to introduce mass production in recent times, the idea was first developed in Venice several hundred years earlier, where ships were mass-produced using pre-manufactured parts, and assembly lines.
During the Industrial Revolution simple mass production techniques were used at the Portsmouth Block Mills to manufacture ships' pulley blocks for the British Navy during the Napoleonic Wars. It was also used in the manufacture the of clocks and watches, and in the manufacture of small arms.