be positioned relative to a datum feature at MMC. See Fig. 5-8. Where datum feature B is at MMC, its axis determines the location of the pattern of features as a group. Where datum feature B depart» from MMC, its axis may be displaced relative to the location of the datum axis (datum B at MMC) in an amount equal to one-half the difference between its actual mating size and MMC size.
NOTE: If a functional gage is used to check the part, this *hift of the axis of the datum feature is automatically accommodated. However, if open set-up inspection methods are used lo check the location of the feature pattern relative to the axis of the datum feature's actual mating envelope, this must be taken into account.
Since the axis of the datum feature's actual mating envelope must serve as the origin of measurements for the pattern of features, the features are therefore viewed as if they, as a group, had been displaced relative to the axis of the datum feature's actual mating envelope. This relative shift of the pattern of features, as a group, with respect to the axis of the datum feature does not affect the positional tolerance of the features relative to one another within the pattern.
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