What does a diameter symbol in a positional tolerance indicate?

What does a diameter symbol in a positional tolerance indicate?

• A. The tolerance zone is a cylinder around the true position with that diameter.
• B. The tolerance zone is a sphere around the true position.
• C. It indicates a square tolerance zone.
• D. It defines the maximum material condition.

Answer: (A)

The diameter symbol attached to a positional tolerance defines a right circular cylindrical tolerance zone around the true position. This means the axis of the feature (such as a hole or a pin) must lie within a cylinder whose diameter equals the specified tolerance. The centerline can deviate radially from the true position by up to half of that diameter, in any direction, while the orientation and location are tied to the datum references. The cylinder’s axis is aligned with the true position, giving a circular, symmetrical tolerance envelope in 3D. If you saw a sphere or a square instead, those shapes would indicate different kinds of tolerance zones, but for a positional tolerance the diameter symbol always denotes this cylindrical zone.

The diameter symbol attached to a positional tolerance defines a right circular cylindrical tolerance zone around the true position. This means the axis of the feature (such as a hole or a pin) must lie within a cylinder whose diameter equals the specified tolerance. The centerline can deviate radially from the true position by up to half of that diameter, in any direction, while the orientation and location are tied to the datum references. The cylinder’s axis is aligned with the true position, giving a circular, symmetrical tolerance envelope in 3D. If you saw a sphere or a square instead, those shapes would indicate different kinds of tolerance zones, but for a positional tolerance the diameter symbol always denotes this cylindrical zone.