RFS Applied to a Pattern of Holes

In Fig. 5-11, the six holes may vary in size from 25 to 25.6 diameter. Each hole must be located within the specified positional tolerance regardless of the size of that hole. A hole at LMC (25.6 diameter) is

as accurately located as a hole at MMC (25 diameter). This positional control is more restrictive than the MMC principle. Datum Features at RFS. The functional requirements of some designs may require that RFS be applied to a datum feature. That is, it may be necessary to require the axis of an actual datum feature (such as datum diameter B in Fig. 5-11) to be the datum axis for the holes in the pattern regardless of the datum feature's size. The RFS application does not permit any shift between the axis of the datum feature and the pattern of features, as a group, where the datum feature departs from MMC.

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