At times, you may find it necessary to force the extension lines to take on mangle other than 90° to the dimension line. This is a common requirement of isometric drawings, where most lines are at 30° or 60° angles instead of 90 degree .To fadlitate nonorthogonal dimensions like these, AutoCAD offers the Oblique option. .
- Choose Dimension > Oblique, or type Ded.You can also select Dimension Edit tool from the Dimension toolbar, and then type O.
- At the Select object prompt, pick the aligned dimension at the upper-right of the drawing and press button to confirm your selection:
- At the Enter obliquing angle (Press enter for none): prompt,enter 60 for 60 degrees. The dimension will skew so that the extension lines are at .60°, as shown in Figure 9.20.
- Exit AutoCAD. You are done with the tutorials in this chapter.
Applying Ordinate Dimensions
In mechanical drafting, ordinate dimensions are used to maintain the accuracy of machined parts by establishing an origin on the part. All major dimensions are described as x-coordinates or y-coordinates of that origin. The origin is usually an easily locatable feature of the part, such as a machined bore or two machined surfaces. Figure 9.21 shows a typical application of ordinate dimensions. In the lower-left comer, note the two dimensions whose leaders are jogged. Also note the origin location in the upper-right comer.
To use AutoCAD’s Ordinate Dimension command, perform the following steps.
- Click Tools > UCS > Origin, or type UCS.
- At the Specify new origin point <0.0,0>: prompt, click the exact location of the origin of your part.
- Toggle the Ortho mode on.
- Click the Ordinate Dimension tool on the Dimension toolbar, You can also enter Dor to start the ordinate dimension.
- At the Select feature location: prompt, click the item you want to dimension.
- At the Specify leader endpoint or [Xdatum/Ydatum/Mtext/Text/Angle] : prompt, indicate the length and direction. of the leader. Do this by positioning the rubber-banding leader perpendicular to the coordinate direction you want to dimension, and then clicking that point.
In steps 1 and 2, you used the UCS feature to establish a second origin in the drawing. The Ordinate Dimension tool then uses that origin to determine the ordinate dimensions. You will get a chance to work with the UCS feature in Chapter 16.
You may have noticed options in the Command window for the Ordinate Dimension tool the Xdatum and Ydatum options force the dimension to be of the x- or y-coordinate no matter what direction the leader takes. The Mtext option opens the Multiline Text Editor, allowing you to append or replace the ordinate dimension text, The Text option lets you enter a replacement text directly through the Command window.