In geometric dimensioning and tolerancing, true position control uses a cylindrical tolerance zone projected to the datums; what does it constrain?

• A. The diameter tolerance of the feature independent of datums.
• B. The surface finish specification.
• C. The overall part length tolerance only.
• D. The cylindrical tolerance zone around the true position projected to the datums, constraining X and Y location and orientation relative to datum axes.

Answer: (D)

True position control defines where a feature should sit in relation to the datum reference frame, using a cylindrical tolerance zone that is centered on the feature’s axis. When this zone is projected to the datums, it enforces how far the feature’s axis can deviate in the plane perpendicular to the axis and how much the axis can tilt relative to the datum axes. In practical terms, this means the feature’s X and Y location and its orientation with respect to the datum directions are constrained. It does not govern the feature’s length, surface finish, or the feature’s diameter by itself (those are controlled by other tolerances).