Placing the datum symbol on the opposite side of a dimension arrow indicates that the datum is the centerplane (or axis for cylindrical parts) of the associated dimension.

Jul 11, 2025 · In GD&T, a datum is a theoretically perfect point, axis, or plane that serves as a reference for measuring and manufacturing parts. While actual part features may have imperfections, datums …

In engineering and drafting, a datum is a reference point, surface, or axis on an object against which measurements are made. These are then referred to by one or more 'datum references' which …

Nov 5, 2025 · The datum axis is a reference that provides a theoretical centerline from which the location and orientation of other features are precisely controlled. The datum axis is a perfectly …

Mar 16, 2024 · A Datum is a plane, axis, or point location that GD&T dimensional tolerances are referenced to. Typically, multiple features will be referenced by each datum, so they're a very …

A datum line can be a datum axis or datum axis line. A datum line is generally established on the center of a target’s cylinder bore or cylinder shaft, and is rarely established on a ridge.

The dimension line of a datum feature and the datum are indicated apart from each other. The centre of the indicated datum feature becomes the datum axis or datum centre plane.

Jan 2, 2025 · What’s the difference between a datum axis and a datum point or plane? A datum axis is a theoretical centerline, based on cylindrical features, which controls four degrees of freedom.

Oct 9, 2024 · A flat surface or an axis can serve as datum A. For example, for a part with a flat surface, the flat bottom can be datum A. Datum B is perpendicular to datum A.

Apr 30, 2025 · Datum: The theoretical plane, point, or axis derived from a datum feature. For example, the center of a hole is the datum feature; the axis running through the center is the datum.