How are datums referenced in a FCF?

How are datums referenced in a FCF?

• A. Datums are listed after the tolerance value in the FCF, typically like A, B, C.
• B. Datums are listed before the tolerance value in the FCF.
• C. Datums are not used in the FCF.
• D. Datums appear after the datum reference frame is constructed.

Answer: (A)

In a GD&T Feature Control Frame, the datum references come after the tolerance specification. This order defines the Datum Reference Frame (DRF) that the control uses to constrain the feature, with the datums listed in the sequence of priority (primary, secondary, tertiary). So a frame reads something like the geometric symbol, then the tolerance value, followed by the datum letters A, B, C. This placement ties the permissible variation directly to the established datums, guiding how the part is oriented and located when inspected. The other options don’t fit standard practice because datums are indeed used in a FCF, and they are not positioned before the tolerance or after the frame is constructed.

In a GD&T Feature Control Frame, the datum references come after the tolerance specification. This order defines the Datum Reference Frame (DRF) that the control uses to constrain the feature, with the datums listed in the sequence of priority (primary, secondary, tertiary). So a frame reads something like the geometric symbol, then the tolerance value, followed by the datum letters A, B, C. This placement ties the permissible variation directly to the established datums, guiding how the part is oriented and located when inspected. The other options don’t fit standard practice because datums are indeed used in a FCF, and they are not positioned before the tolerance or after the frame is constructed.