Standarddatumplanen

Standarddatumplanen denotes a standardized set of datum planes used as reference geometry in mechanical design, manufacturing, and inspection. They provide a common frame of reference for describing the orientation, location, and tolerances of features on a part. Typically, the minimal set includes three mutually perpendicular planes—a primary, a secondary, and a tertiary datum plane—often labeled A, B, and C or mapped to Cartesian planes XY, YZ, ZX. In more complex parts, additional planes may be defined.

Purpose and use: Datum planes form the basis for geometric dimensioning and tolerancing (GD&T). They fix part orientation in assembly and measurement, enabling consistent data exchange between design, manufacturing, and inspection systems. They also support coordinate transformations between CAD models, CAM data, and metrology equipment.

Standards and variation: The practice is codified in international standards such as ISO 1101 and ASME Y14.5. While the concept of datum planes is universal, the naming, order, and criteria for selecting datums vary by industry and standard. Some applications require extra planes to control specific features.

Implementation: In design, engineers choose datum planes based on function, manufacturability, and measurability. In CAD, datum planes are created and linked to datum features, used to orient geometry and drive inspection plans. In production, the datum system guides setup and probing strategies during metrology.

See also: Geometric dimensioning and tolerancing, Datum (geometry), Coordinate system, Datum feature.