This feature control frame specifies the tolerance zone as a circle of diameter .010 at MMC, centered according to the basic dimensions given. The size of the tolerance zone is dependent on the size of the hole.
A feature control frame can specify the size of the tolerance zone at MMC, LMC or RFS (regardless of feature size).
Tolerance Zone diameter
Determining Tolerance Zone Size
Does this feature meet the true position tolerance?
Step 1: What can we measure?
Calculate deviations in x and y directions. How does this compare to the basic dimensions?
Step 3: Determining the True Position
Tolerance zone, dia. = TZ
Desired position Actual hole center
A hole center that deviates from true position by jc and y lies within a tolerance zone of diameter Z. If Z > TZ, the part is bad.
015 014 013 012 Oil 010
008 it Q
True Position and Perpendicularity
This feature control frame specifies the true position tolerance of the hole with respect to 3 datum planes. The order that the datum planes are listed in the feature control frame indicates the priority of each datum. Datums B and C provide reference for the x and y position of the hole center, and datum A controls the perpendicularity of the hole axis .
Referencing datum A means that the center axis of the hole must be perpendicular to datum plane A. The axis must intersect datum plane A inside the tolerance zone
Permissible hole axis variation
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