Conditions: Geometric parameters include size, geometric shape, mutual position, surface roughness, angle and taper, etc. Mechanical and physical performance parameters usually refer to hardness, strength and stiffness. It is impossible and unnecessary for various parameters of machine parts to reach absolutely accurate values. As long as the actual values are kept within the specified range, the technical requirements can be met. The allowable deviation specified by the parameter value is called tolerance.
In terms of use, for example, the parts of bicycles and watches that people often use, and the parts of various equipment used in production, when they are damaged, the repairman can quickly replace them with parts of the same specification to restore the functions of bicycles, watches and equipment.
In some cases, the function of interchangeability is still difficult to measure by value. For example, on the battlefield, it is absolutely necessary to eliminate the failure of weapons and equipment immediately and continue fighting.
From the manufacturing point of view, interchangeability is a powerful means to improve the production level and carry out civilized production. There is no need for auxiliary processing and repair during assembly, so it can reduce the labor intensity of assembly workers, shorten the assembly cycle, and make assembly workers work in one process, thus automatically assembling, thus greatly improving street efficiency.