2024年3月16日 · 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 important part of the whole thing.

A datum feature can be a plane, line, or point, which needs to be used selectively depending on the tolerance and feature you need to specify. This page explains the indication symbols and how to establish datums, using three datums, i.e. the datum plane, datum line, …

2025年1月2日 · A datum axis is a theoretical centerline, based on cylindrical features, which controls four degrees of freedom. On the other hand, datum points and planes, which are normally designed from locations or flat surfaces control fewer degrees of freedom.

2023年8月11日 · The axis of this perfect cylinder is the datum axis. To simulate this with measurement equipment, we could use a 3-jawed chuck, as shown in Figure 2, below. This chuck engages the highpoints of the cylinder, and when we rotate this part, we …

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 indicate measurements that should be made with respect to …

2023年4月11日 · ASME Y14.5 (1994) defines a datum as “A theoretically exact point, axis, or plane derived from the true geometric counterpart of a specified datum feature. A datum is an origin from which the location or geometric characteristics of features of a part are established.”

Primary Datum (Datum A) The primary datum typically constrains three degrees of freedom. This datum is usually a large, flat surface or stable feature that restricts: Movement along the Z-axis (up and down). Rotation around the X-axis (forward/backward tilt). Rotation around the Y-axis (side-to-side tilt).

4 天之前 · A: In Geometric Dimensioning and Tolerancing (GD&T), datums provide the measurement and manufacturing processes with a reference system using the part’s features. A datum is a theoretically exact point, axis, or plane which can be obtained from the true geometry of a specified datum feature.

2024年10月9日 · 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. It defines two more DoFs.

Datum Axis - the datum axis is the theoretically exact centerline of the datum cylinder as established by the extremities or contacting points of the actual datum feature cylindrical surface, or the axis formed at the intersection of two datum planes.