Circular and Cylindrical Targets

Circular target lines and cylindrical target areas may be used to establish a datum axis on rotating parts. See Fig. 4-36.

4.6.5 Secondary Datum Axis. For a secondary datum feature (RFS), a set of thicc equally spaccd targets may be used to establish a datum axis. See Fig. 4-37. The centering device used to establish the datum axis has a set of three equally spaced contacting features capable of moving radially at an equal rate from a common axis that is perpendicular to the primary datum plane. In this example, the datum targets and the contacting features are oriented relative to a tertiary datum feature.

4.6.6 Equalizing Datums. Where a part configuration is such that rounded features on opposite ends are used to establish datums, pairs of datum target points or lines are indicated on these surfaces, as in Fig. 4-38. Equalizing pin locations arc intended where target points are coordinately dimensioned. V-type equalizers are intended where target points are defined by angles shown tangent to the surface. Where target lines are defined by a dimension from another datum plane, as in Fig. 4-38 for lines B1 and B2, knife edge V-type equalizers are intended, whereas V-type planes may be indicated by only showing the lines in the top view. Equalizing datums may be applied to other suitable part configurations. It is permissible, in such a case, to use the datum feature symbol to identify the equalized theoretical planes of the datum reference frame. It should be noted however, that this is an exception, and is to be

Datum DimensioningDrawing With Positional Tolerancing

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  • Primrose
    What is an equalized datum target?
    8 years ago

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