To verify multiple holes in a pattern, what provides the orientation and location reference?

• A. A datum target.
• B. A true position callout.
• C. A projection tolerance zone.
• D. A datum reference frame provides the orientation and location reference for verifying hole axes.

Answer: (D)

A datum reference frame provides the orientation and location reference for verifying hole axes. It establishes a coordinate system tied to designated datum features on the part, so measurements of the hole pattern are made consistently relative to that frame. This lets you evaluate the true position of each hole axis against the tolerance with the same orientation and origin every time, independent of how the part sits on the table or how the measurement setup is approached.

Datapoints like datum targets are used to help locate and establish datums but don’t themselves define the measurement frame. The true position callout specifies how far the hole axes may deviate from their ideal locations, i.e., the tolerance, rather than creating the common reference frame. A projection tolerance zone describes a depth-specific tolerance for projecting features, not the overall orientation and location reference for the pattern.