Which tolerance category controls the actual shape of a feature boundary?

• A. Profile tolerances
• B. Runout tolerances
• C. Location tolerances
• D. Form tolerances

Answer: (D)

Understanding how a feature boundary should look in shape is what form tolerances address. They specify the allowable deviation of the boundary from its true geometric form, independent of where the feature sits or how it’s oriented. That means they control the actual shape of the boundary itself—things like straightness, flatness, circularity, and cylindricity. For example, a flatness tolerance draws a boundary that must fit between two parallel planes, ensuring the surface boundary remains truly flat. Other tolerance types are about different aspects: profile ties the boundary to a theoretical outline of a surface and can involve position or orientation relative to a datum; runout blends shape with rotation around a datum axis; location fixes where the boundary sits relative to datums. But to pin down the pure shape of the boundary itself, form tolerances are the ones that govern that aspect.