INTERCHANGEABILITY

Interchangeability is the capacity to produce components that are sufficiently precise and standardized to be assembled without individual fitting, and replaced by an identical part when needed. It requires controlled manufacturing tolerances, ensuring that any part chosen at random from a batch fits correctly with its counterpart. In watchmaking, this notion became established at the end of the 19th century with the industrialization of production: it enabled a shift from artisanal manufacturing, where each part was hand-fitted for a given Movement, to economical series production and after-sales service through the exchange of spare parts. Interchangeability relies on metrology, standardization (gauges, standards, NIHS norms) and the precision of machines. As a founding principle of modern watchmaking, it determines the costs, repairability, and reliability of watches alike. Its downside is a certain standardization, which high-end watchmaking compensates for through finishing and manual adjustments on parts that are nonetheless interchangeable.