Error and tolerance of precision parts machining

Tolerance refers to the maximum value of error that can be accepted in this industry as specified in the standard. The geometric parameters of precision parts machining have a variable momentum, that is to say, there is a range of allowable machining error. The allowable variation is called tolerance, that is, the machining process generally only needs to meet the tolerance.

In the actual production process, the geometric parameters of parts with the same specification cannot be absolutely accurate and consistent due to the influence of equipment accuracy, tool wear, measurement error, and the operation level of workers. The difference of size, shape and position of precision parts after machining is called machining error.

Two different parts are assembled together, for example, the assembly of shafts and holes of the same size requires a little looseness and a little tightness. The requirement of this tightness is a kind of fit relationship, and the tolerance and fit are related to each other.