Creating Half-Dimensions

Half-Dimensions are useful in the case of revolved features or elements using a plane symmetry. Actually it allows to create the dimensions only on half the geometry.

This task will show you how to create a half-dimension. You can create half-dimensions on distance, angle, diameter, cylinders, diameter edges and diameter tangents but not on cumulate dimensions.

Open the Brackets_views05.CATDrawing document.

Click the Dimensions icon from the Dimensioning toolbar.

Click a first element in the view. For example, an edge.

If needed, click a second element in the view. For example, another edge.

Right-click the dimension and select the Half Dimension option from the contextual menu.

The half-dimension appears. Only one extension line is displayed. The dimension line is shortened with specific overrun, gap and length. The value is not centered on the dimension line. The attributes mentioned in Dimension parameters drive the dimension graphic display.

	Once you select the half-dimension option from the contextual menu, all the following dimensions you create will be assigned the half-dimension mode. If you want to create dimensions in the standard mode, go back to the contextual menu and de-activate the Half Dimension option.
	You can create a half-dimension directly by selecting first an axis line and then an other element (which is not an axis). The half-dimension value will be the double of the measured value between the elements. If you don't want a half-dimension to be created when selecting such elements, uncheck Half Dimensions from the contextual menu (right-click) when creating the dimension.

Associativity in the case of half-dimensions is different from associativity in the case of standard dimensions. For example, the half diameter dimension below is associated to the axis and the element, whereas a standard diameter is associated to both symmetrical elements.

Standard diameter edge:

Half diameter edge: