The letters indicating the datums are always oriented to the direction the reader looks at the drawing. Datum symbols use either a white or black triangle. Drawing Indications of Datum Featuresĭatums are indicated using the following symbols (datum symbols). Therefore, a surface plate, gauge, or mandrel, which has a more precise surface, must come into contact as a simulated datum.Į Surface plate, gauge, mandrel, etc. The surface of a part indicated as a datum is not an exact shape. Datum System A group of datums created by combining more than one individual datum in order to use it as a reference for toleranced features. Simulated Datum Feature An actual surface with sufficiently precise shape that comes into contact with a datum feature and is used for establishing a datum (e.g. Datum Feature A real (non-ideal) integral feature of a target used for establishing a datum (e.g. Multiple datums can also be combined to make a datum system that specifies a feature.
#STANDARD DATUM PLANE ISO#
A datum is a plane, a straight line, or a point that is used as a reference when processing a material or measuring the dimensions of a target.Ī datum is defined as follows in the ISO standard: ISO 5459：2011 “One or more situation features of one or more features associated with one or more real integral features selected to define the location or orientation, or both, of a tolerance zone or an ideal feature representing for instance a virtual condition.” Types of Datumsĭatums are established using datum features and simulated datum features.
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