What is the purpose of a datum target?

• A. A defined point/area used to establish a datum when the datum surface is not readily accessible.
• B. A measurement device used to calibrate datums.
• C. A color code for datum surfaces.
• D. A tolerance zone used for indexing.

Answer: (A)

In GD&T, a datum provides a fixed reference frame for locating features. When the actual datum surface isn’t easily accessible—it may be recessed, inside a hole, or obscured—you still need a way to establish that reference. A datum target is that defined point or area on an accessible portion of the part, positioned in a known relationship to the true datum surface, that serves to establish the datum. By specifying and using this target, measurements and setups can be repeated consistently even though the real surface can’t be touched directly. Datum targets are not measurement devices, color codes, or tolerance zones; they are reference points tied to the datum feature to ensure repeatable alignment and measurement.