What is the primary purpose of including datums in GD&T for assembly?

What is the primary purpose of including datums in GD&T for assembly?

• A. Provide reference points for measurement and assembly
• B. Define material hardness
• C. Determine thread pitch
• D. Dictate material selection

Answer: (A)

Datums in GD&T establish a fixed datum reference frame anchored to the functional mating surfaces of a part. This frame provides a consistent origin and orientation for all measurements and tolerances, so dimensions and features are interpreted the same way during inspection and assembly. In assembly, this means parts align and fit predictably because every feature is located and oriented relative to the same reference frame, reducing ambiguity from part-to-part variation. Datums are not used to specify material hardness, thread pitch, or material selection.

Datums in GD&T establish a fixed datum reference frame anchored to the functional mating surfaces of a part. This frame provides a consistent origin and orientation for all measurements and tolerances, so dimensions and features are interpreted the same way during inspection and assembly. In assembly, this means parts align and fit predictably because every feature is located and oriented relative to the same reference frame, reducing ambiguity from part-to-part variation. Datums are not used to specify material hardness, thread pitch, or material selection.