Which of the following is an example of a datum feature?

• A. A flat surface
• B. A gauge pin
• C. A datum target
• D. A chamfer

Answer: (A)

Datum features are the actual parts of the object that establish the datum reference frame used for GD&T. A flat surface is a classic datum feature because it provides a well-defined plane on the part itself, giving a stable and measurable reference for orientation and location. The gauge pin isn’t part of the component; it’s a measuring tool used during inspection, so it doesn’t establish a datum on the part. A datum target helps locate or measure the datum but isn’t the datum feature on the part itself. A chamfer is just an edge modification and, unless specifically designated as a datum feature, doesn’t provide the stable reference surface or plane needed for a datum.