Info

from datum B

00.8 pattern-locating tolerance zone cylinders (6 zones, basically related to each other, basically located to the datums)

Actual feature axes must simultaneously lie within both tolerance zones

One possible displacement of actual feature pattern.

FIG. 5-20 HOLE PATTERNS OF FIG. 5-19 WITH SECONDARY DATUMS IN FEATURE-RELATING SEGMENTS OF COMPOSITE FEATURE CONTROL FRAMES {CONTD) Tolerance Zones for Slx-Hola Pattern to datum plane A and therefore, parallel to each other. In certain instances, portions of the smaller zones may fall beyond the peripheries of the larger tolerance zones. However, these portions of the smaller tolerance zones are not usable because the axes of the features must not violate the boundaries of the larger tolerance zones. The axes of the holes must lie within the larger tolerance zones and within the smaller tolerance zones. The axes of the actual holes may vary obliquely (out of perpendicularity) only within the confines of the respective smaller positional tolerance zones (FRTZF). Figure 5-19(e) repeats the heretofore-described relationships for the four-hole pattern, and Fig. 5-19(f) for the six-hole pattern of features shown in Fig. 5-19.

NOTE: The zones in Figs. 5-19 and 5-20 are shown as they exist at MMC of the featureĀ«. The large zones would increase it size by the amount the features depart from MMC, as would the smaller zones: the two zones are not cumulative.

5.4.1.2 Primary and Secondary Datums Repeated in Lower Segment. Figure 5-20 repeats the hole patterns of Fig. 5-19. In Fig. 5-20, the lower segment of the composite feature control frame repeats datums A and B. Figure 5-20(c) shows that the tolerance cylinders of the FRTZF may be displaced from the true position locations (as a group) as governed by the tolerance cylinders of the PLTZF, while remaining perpendicular to datum plane A and parallel to datum plane B. Figure 5-20(d) shows that the actual axes of the holes in the actual feature pattern must reside within both the tolerance cylinders of the FRTZF and the PLTZF. Figure 5-20(e) repeats the heretofore-described relationships for the four-hole ex 0iof*

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