20.1.1 Restricted range of application

Figures 20.1 and 20.2 show examples of restricted ranges of application of geometrical tolerances.

Figure 20.1: Restricted application of perpendicularity tolerance

Figure 20.2: Restricted application of run-out and roundness tolerance

20.1.2 Geometrical tolerances and additional smaller tolerances of their components

It may be that, besides the geometrical tolerances, their components may have to have narrower tolerances. For example, journal shafts may require smaller tolerances for roundness than for cylindricity in order to maintain proper lubrication (Fig. 20.3).

Figure 20.3: Cylindricity tolerance and smaller tolerance of its component roundness

According to Fig. 20.4, the surface of the right cylinder may vary between two cylinders coaxial with the datum A. According to Fig. 20.5, the parallelism deviation (and the straightness deviation) of the generator lines are restricted to a smaller tolerance (0.05).

Figure 20.4: Total run-out tolerance

Figure 20.5: Run-out tolerance and smaller tolerance of parallelism of the generator lines

20.1.3 Superposition of positional tolerances

Figure 20.6 shows two groups of holes. The four hole group is related to the datums D, A and B. The maximum material virtual conditions ( ?7.85) of this group together establish the datum C of the positional tolerances ?0.15 of the three hole group. That is, perpendicular to D, the maximum material virtual condition of the four holes ( ?7.85) together with the maximum material conditions of the three holes ( ?5.75) must fit (simultaneously) into the holes. In addition, perpendicular to...