In GD&T, what does the symbol Ø indicate?

In GD&T, what does the symbol Ø indicate?

• A. The tolerance zone is a cylinder of the specified diameter around the axis.
• B. It indicates a flatness requirement.
• C. It denotes a radial dimension.
• D. It represents a circular runout condition.

Answer: (A)

Ø is the diameter symbol. In GD&T, when you see this symbol ahead of a tolerance value, it means the tolerance zone is circular in cross-section—a cylinder with that diameter. The axis of that cylinder is aligned with the feature’s axis (or the datum axis used for the control), so the controlled axis must stay within a cylindrical zone of the specified diameter around the true position axis. In practical terms, any allowed deviation is a radial one, up to radius equal to diameter/2, in any direction around the axis. This is why this symbol is used to define a cylindrical tolerance zone for features like holes or pins. It does not indicate flatness, a simple radial dimension, or circular runout, which use different symbols or concepts.

Ø is the diameter symbol. In GD&T, when you see this symbol ahead of a tolerance value, it means the tolerance zone is circular in cross-section—a cylinder with that diameter. The axis of that cylinder is aligned with the feature’s axis (or the datum axis used for the control), so the controlled axis must stay within a cylindrical zone of the specified diameter around the true position axis. In practical terms, any allowed deviation is a radial one, up to radius equal to diameter/2, in any direction around the axis. This is why this symbol is used to define a cylindrical tolerance zone for features like holes or pins. It does not indicate flatness, a simple radial dimension, or circular runout, which use different symbols or concepts.