How does "concentricity" differ from "position" tolerance?

• A. Concentricity controls the alignment of an axis to a datum axis; position controls the location of a feature's axis or center relative to datums.
• B. Concentricity controls the alignment of an axis to a datum axis; position controls the location of a feature's axis or center relative to datums.
• C. Concentricity is a type of tolerance that determines color.
• D. Position tolerance controls the circularity of a feature.

Answer: (B)

Concentricity is about coaxial alignment: the axis of the feature must run along the same axis as the datum feature. The tolerance zone is a cylinder coaxial with the datum axis, so it limits how far the feature’s axis can deviate from being perfectly aligned with that datum axis. It doesn’t directly fix where the axis sits in space, only how well it lines up with the datum.

Position tolerance, by contrast, controls where the center or axis of the feature is located relative to datums. Its tolerance zone is defined in true position and constrains the feature’s location rather than its axial alignment.

So the correct idea is that concentricity governs axis alignment to a datum axis, while position governs the location of the feature’s axis or center relative to datums. (Color or circularity concepts don’t apply here.)