How does a profile tolerance interact with datums?

How does a profile tolerance interact with datums?

• A. It always references a primary datum.
• B. It can only be independent.
• C. It defines a feature's size relative to datums.
• D. It can be independent or referenced to datums; the relation to datums is defined in the FCF.

Answer: (D)

The key idea is that a profile tolerance can be applied with or without tying it to a datum reference frame. When you place a profile control frame, you decide whether the profile of the surface must lie within the tolerance zone relative to datums, or whether it is allowed to float independently of datums. If datums are included in the control frame, the profile is constrained by that datum reference frame—the zone’s orientation and location are defined with respect to the specified datums. If no datums are referenced, the profile simply must stay within the tolerance zone without any datum-based constraint. The exact relationship to datums is specified in the feature control frame, which determines which datums are used and how the profile is constrained. So this tolerance can be independent or datum-referenced, with the specific choice defined in the FCF.

The key idea is that a profile tolerance can be applied with or without tying it to a datum reference frame. When you place a profile control frame, you decide whether the profile of the surface must lie within the tolerance zone relative to datums, or whether it is allowed to float independently of datums. If datums are included in the control frame, the profile is constrained by that datum reference frame—the zone’s orientation and location are defined with respect to the specified datums. If no datums are referenced, the profile simply must stay within the tolerance zone without any datum-based constraint. The exact relationship to datums is specified in the feature control frame, which determines which datums are used and how the profile is constrained. So this tolerance can be independent or datum-referenced, with the specific choice defined in the FCF.