Which statement accurately defines a basic dimension?

Which statement accurately defines a basic dimension?

• A. An exact dimension used to locate features; it has no tolerance and is boxed.
• B. A dimension that has a tolerance.
• C. A diameter dimension.
• D. A dimension used to specify effort.

Answer: (C)

In GD&T, a basic dimension is an exact value used to locate features or establish true positions, with no tolerance applied to it. It is shown in a rectangular box. The idea is that the tolerance for how far a feature can vary is defined by a geometric dimensioning control frame (like position) attached to the feature, not by the basic dimension itself. So the statement that describes an exact dimension used to locate features, with no tolerance and boxed, is the correct way to define a basic dimension. The other options describe dimensions with tolerances, generic diameter callouts, or irrelevant concepts, none of which capture the basic dimension concept.

In GD&T, a basic dimension is an exact value used to locate features or establish true positions, with no tolerance applied to it. It is shown in a rectangular box. The idea is that the tolerance for how far a feature can vary is defined by a geometric dimensioning control frame (like position) attached to the feature, not by the basic dimension itself. So the statement that describes an exact dimension used to locate features, with no tolerance and boxed, is the correct way to define a basic dimension. The other options describe dimensions with tolerances, generic diameter callouts, or irrelevant concepts, none of which capture the basic dimension concept.