Fits Between the Shaft and the Hub and Fits Between the Hub and the Shaft

Abstract

The productions of shafts and hubs cannot strictly be made to a precise dimension without causing a rise in the production costs; therefore any variations in the indicated dimension, must be taken into account. The indicated dimension, which acts as a reference dimension, is the nominal dimension. The higher the required degree of accuracy, the smaller are the deviations relative to such dimension, even if a considerable price rise is involved. Another reason where the deviations from the nominal dimension are acceptable is that it is possible to produce connections made up of a shaft and a hub which can be mounted or dismounted or not. There is not a question of accepting tolerances on one of the components, but rather of producing tightened or clearance that can be mounted or dismounted according to working requirements. The tolerances have been standardized in system ISO based on the following principles:

• (1) The qualities are classified on the basis of numbers ranging from 1 to 16; the lowest degree of quality corresponds to the highest number. The qualities worth values of 0 and 01 have been produced in case an extremely high degree of accuracy is required.

• (2) Diameters are classified according to different intervals. The diameter calculated by the geometrical average of the interval is characterized by the calculation of the tolerances.