![]() ![]() ![]() The position of the datum symbol on the drawing is also relevant to the target area. 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. 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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