How do you interpret a dimension labeled Ø0.010 in GD&T?

• A. The feature must be a cylinder with 0.010 height.
• B. The surface is within flatness 0.010.
• C. The feature is located within 0.010 from datum.
• D. The feature has a cylindrical tolerance zone around its axis with diameter 0.010.

Answer: (D)

In GD&T, the diameter symbol before a size signals a cylindrical tolerance zone around the feature’s axis. A value of 0.010 means that the tolerance zone is a cylinder with a diameter of 0.010, coaxial with the feature’s axis. The surface of the feature must lie within that cylinder, so the axis can wander but the surface must stay within 0.005 on either side of the true axis. This interpretation governs form or runout aspects that use a cylindrical zone, not height, flatness, or positional distance from a datum. The other options pull in concepts (height, flatness, location) that aren’t defined by a Ø dimension alone.