- The term Interchangeability is normally employed for the mass production of identical items within the limits of its dimension and size.
- In order to control the size of a finished part another part is developed which must be interchangeable called as Limit Systems.
When an assembly is made of two parts the part which enter into the other called as Enveloping Surface and the hole in which it entered called Enveloped Surface.
It is the difference between the basic dimension of the mating parts .When the shaft size is less than the hole size, it called Positive Allowance and when it is greater than the hole size called Negative Allowance.
- Tolerance is the difference between upper limit and lower limit of the dimension of a shaft .It otherwise defined as maximum permissible variation in dimension.
- The region in which tolerance occurs called as tolerance zone