Engineering Definition
Datum
A theoretically exact reference plane, axis or point used to establish the coordinate framework for geometric tolerances and inspection.
Why it matters
Datum selection determines how a part is constrained, measured and related to its functional interfaces.
Related technical topics
Technical Literacy · Intermediate
Geometric Dimensioning and Tolerancing (GD&T)
Understand how GD&T communicates allowable geometric variation using datums, feature-control frames and standardized controls for form, orientation, location and runout.
Metrology & Quality · Intermediate
Coordinate Measuring Machines (CMMs)
Understand CMM fundamentals, probing, alignment, datum establishment and how inspection programs translate drawing requirements into measured results.
Machining & CNC · Intermediate
Workholding, Fixtures and Jigs
Learn how vises, chucks, clamps, locators, fixtures and jigs establish part position and resist process forces while supporting repeatability.