What is form fit?

Form fit is a type of fit between two mating components (for example, two gears, two shafts, or a shaft and a bearing) that involves a very precise relationship between their sizes and shapes. In a form fit, the mating components are designed so that they match each other's contours exactly, eliminating any looseness or play between them. Form fit is often used where accurate positioning, alignment, or stability is important, such as in high-precision machines, engines, or aerospace applications. Some common types of form fits include interference fits, clearance fits, and transition fits, each of which describes a specific range of tolerances between the mating components. The proper selection of a form fit requires careful consideration of factors such as material properties, surface finish, temperature, and load conditions to ensure that the components will function properly and reliably.