When a feature of a part is used as a reference for measurement, it is termed what?

When a feature of a part is designated as a reference for measurement, it is classified as a datum feature. A datum feature serves as a specific surface, line, or point from which measurements can be taken to ensure accuracy and consistency in the manufacturing and inspection processes. This is critical in engineering and manufacturing as it establishes a standard point of reference, ensuring that multiple parts can be aligned, measured, and compared against a common framework.

Datum features play a vital role in Geometric Dimensioning and Tolerancing (GD&T), where they help define the allowable variation in the part's geometry and ensure that the part functions correctly in the assembly. For instance, when evaluating the alignment of holes in a component, the datum feature provides a stable foundation from which to measure the position of those holes relative to the overall design.

Understanding that a datum feature is essential for maintaining precision in fabrication and quality control is crucial for anyone involved in the field of welding or manufacturing.