Which of the following is a form tolerance example?

• A. Perpendicularity
• B. Flatness
• C. True position
• D. Concentricity

Answer: (B)

Form tolerances govern the shape of a feature’s surface, independent of where it sits or how it’s oriented. Flatness is the standard form tolerance because it requires a surface to lie within two parallel planes, constraining only the surface’s shape (its waviness or deviation from a perfect plane). Perpendicularity, on the other hand, sets the angle between a surface or feature axis and a datum, which is an orientation requirement rather than a form check. True position controls where features are located relative to datums, a location tolerance. Concentricity deals with the coaxial relationship of axes, relating more to axis alignment than the surface’s intrinsic form. Therefore, flatness best exemplifies a form tolerance.