These letters are in boxes and tied to the datum feature s with a black triangle. The datum features on a drawing are denoted with a series of capital letters. How Datum Features are Shown on a Drawing They are usually important functional surfaces. ĭatums are theoretical and only simulated by Measurement Equipment (Gauge pins, Granite slabs, angle plates, computer-generated planes, etc)ĭatum Features are real, tangible features on a part where the measurement equipment would physically touch or measure. It is especially important to know this when studying the theories of GD&T and while setting up a Datum Reference Frame. While they are related to one another they are indeed different entities. Its important to know the difference between Datum Features and Datums. It is usually an important functional feature that needs to be controlled during measurement as well.Īll GD&T symbols except for the form tolerances ( straightness, flatness, circularity and cylindricity ) can use datums to help specify what geometrical control is needed on the part. They are the surface or feature where the other features are referenced from. You can think of them as anchors for the entire part. A datum feature is the tangible surface or feature of size ( comprised of multiple surfaces or revolved surfaces) that is indicated by the datum feature symbol. Click on the Datum Feature to access its properties in the panel.Datums are theoretically exact points, axes, lines, and planes or a combination thereof that are derived from datum features.If the Properties panel is already active: Right-click on the Datum Feature then select Item Properties from the context menu. ![]() Double-click on the Datum Feature graphic.To open the Properties panel and access the properties of a placed Datum Feature: The Properties panel when a Datum Feature object is selected. The non-graphical method of editing a Datum Feature is available in the Draftsman Properties panel, which provides editable property fields for the item that is currently selected in the workspace. Properties page: Datum Feature Properties An extension line is added when the attachment point is moved beyond the boundary of the object face. Click and drag the edge attachment node to reposition it along the selected object face.Click and drag the label node to reposition it on the drawing document.When a Datum Feature object is selected, editing handles/nodes become available at its attachment and header label points.Ī selected Datum Feature with its two positioning nodes The graphical method of editing allows a placed Datum object to be selected in the workspace and its edge attachment point or label location changed. The default settings for the Datum Feature object are available in the Draftsman - Defaults page of the Preferences dialog. Move the cursor to set the position of the Datum label then click again to complete placement. ![]()
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