from a common datum reference frame, verification of positional tolerance requirements for the part can be collectively accomplished in a single setup or gage as illustrated by Fig. 5-17. The actual centers of all holes must lie on or within their respective tolerance zones when measured from datums A, B, and C.

NOTE: The explanation given in Fig. 5-17 still applies where independent verification of pattern locations becomes necessary due to size or complexity of the pan. Simultaneous Requirement — MMC. Where any of the common datums in multiple patterns of features is specified on an MMC basis, there is an option whether the patterns are to be considered as a single pattern or as having separate requirements. If no note is added under the feature control frames, the patterns are to be treated as a single pattern. Where it is desired to permit the patterns to be treated as separate patterns, a notation such as SEP REQT is placed beneath each feature control frame. See Fig. 5-18. This allows the datum features of size to establish a separate datum refer ence frame for each pattern of features, as a group. These datum reference frames may shift independently of each other, resulting in an independent relationship between the patterns. This principle does not apply to the lower segments of composite feature control frames except as noted in para.

Was this article helpful?

0 0

Post a comment