What is a datum target?

What is a datum target?

• A. A target on a surface used to establish a datum when the datum surface can't be directly touched.
• B. A basic dimension.
• C. A diameter symbol.
• D. A design note.

Answer: (A)

A datum target is a measurable feature placed on a surface to define a datum when that surface can’t be touched directly by the measuring equipment. In GD&T, datums establish a reference frame for size and form, orientation, and location tolerances. If the actual datum surface is recessed, curved, soft, or otherwise inaccessible, you use targets on the surface as stand-ins. The inspector probes the targets to determine the datum’s exact location and orientation, so the part can be measured consistently relative to that datum. This concept is distinct from basic dimensions, symbols, or purely notes, which do not establish a usable datum via probing targets.

A datum target is a measurable feature placed on a surface to define a datum when that surface can’t be touched directly by the measuring equipment. In GD&T, datums establish a reference frame for size and form, orientation, and location tolerances. If the actual datum surface is recessed, curved, soft, or otherwise inaccessible, you use targets on the surface as stand-ins. The inspector probes the targets to determine the datum’s exact location and orientation, so the part can be measured consistently relative to that datum. This concept is distinct from basic dimensions, symbols, or purely notes, which do not establish a usable datum via probing targets.