In the given example, this implies that the pitch circle and the datum circle must be coaxial, i.e. 20.28įigure 20.29 illustrates a further positional-tolerance application where the geometrical requirement is related to another feature indicated as the datum. In the given example, this implies that the pitch circle and the datum circle must be coaxial, i.e. Specific examples include labeling a datum reference frame origin on a given drawing, sketching datum feature symbols on a drawing given sentence descriptions. 20.28 and no particular datum is specified, then the individual feature to which the geometrical-tolerance frame is connected is chosen as the datum.įigure 20.29 illustrates a further positional-tolerance application where the geometrical requirement is related to another feature indicated as the datum. If a positional tolerance is required as shown in Fig. The reference letters are placed in the third compartment of the tolerance frame, and have a hyphen separating them.įigure 20.26 shows the drawing instruction necessary when the application of the datum features is required in a particular order of priority.įigure 20.27 shows an application where a geometrical tolerance is related to two separate datum surfaces indicated in order of priority. Multiple datums Figure 20.25 illustrates two datum features of equal status used to establish a single datum plane. Note: If there is insufficient space for two arrowheads, one of them may be replaced by the datum triangle, as shown in Fig. When the datum is the axis or median plane or a point defined by the dimensioned feature. The shorter stepped portion Datum B is positioned on an extension line, which is clearly separated from the dimension line.įigure 20.21 shows the datum triangle placed on a leader line pointing to a flat surface.įigures 20.22, 20.23, 20.24 illustrate the positioning of a datum box on an extension of the dimension line, Fig. Datum A is designating the main outline of the feature. No other 2D CAD drafting tool for mechanical design offers an equivalent to the automation found in ARES Mechanical Nesting Manager. ![]() ![]() 20.19 show alternative methods of designating a flat surface as Datum A.įigure 20.20 illustrates alternative positioning of datum boxes. Preparing a drawing to drive metal cutting is a completely manual process in most shops, but ARES Mechanical 2024 offers a better method: Nesting Manager. There is no difference in understanding between solid or blank datum triangles. Datum features are identified on a drawing using a datum feature symbol. ![]() you can right-click on the dwg and get the info through there. Datums are ideal representations of a parts surface, axis or centerplane. The box is connected to a solid or a blank datum triangle. In civil 3D, go to toolspace and settings tab for the current drawing. A datum is designated by a capital letter enclosed by a datum box.
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