Which statement describes a datum feature?

Which statement describes a datum feature?

• A. A theoretical size used to define a model.
• B. A tolerance reference for weight.
• C. A physical feature used to establish a datum (e.g., a flat surface, a bore axis).
• D. A material finish indicator.

Answer: (C)

In GD&T, a datum feature is a real physical feature on the part that is used to establish a datum reference frame. This frame provides the exact location and orientation used to measure and control other features. A datum feature can be something tangible like a finished flat surface that defines a datum plane, or a bore or hole axis that defines a datum axis. The key idea is that the datum feature is the actual feature on the part that is used to reference and locate other features during manufacturing and inspection. The other options don’t fit because they describe concepts that aren’t about establishing a datum reference: a theoretical size used to define a model is a modeling concept, not a physical feature used as a reference; a tolerance reference for weight isn’t how GD&T defines references; and a material finish indicator relates to surface texture, not to establishing a datum.

In GD&T, a datum feature is a real physical feature on the part that is used to establish a datum reference frame. This frame provides the exact location and orientation used to measure and control other features. A datum feature can be something tangible like a finished flat surface that defines a datum plane, or a bore or hole axis that defines a datum axis. The key idea is that the datum feature is the actual feature on the part that is used to reference and locate other features during manufacturing and inspection.

The other options don’t fit because they describe concepts that aren’t about establishing a datum reference: a theoretical size used to define a model is a modeling concept, not a physical feature used as a reference; a tolerance reference for weight isn’t how GD&T defines references; and a material finish indicator relates to surface texture, not to establishing a datum.