So far, you’ve been reading about how to work with linear dimensions. You can also dimension nonorthogonal objects, such as circles, arcs, triangles, and trapezoids. In this section, you will practice dimensioning nonorthogonal objects by drawing an elevation of a window in the set of plans for your studio apartment building. You’ll start by setting up the drawing, then drawing the window itself.
- Create a new file called Window.
- ln the Create New Drawing wizard, click the Start From Scratch icon at the top, then click the English radio button if you are using feet and inches or click the Metric radio button. This is important because depending on which option you select, AutoCAD will set up the drawing with different dimension style defaults, AutoCAD will create a style called ISO-25 as the default style for metric users.
- If you are using the English measurement system, start by setting the dimension scale to 4. Normally, you would use the Dimension Style Manager dialog box to set the dimension scale. A shortcut to do this is by typing Dimscale. This changes the scale factor of the current dim,ension style to 4, Metric users can use the default setting.
- There are two more settings that English system users should set. Enter Dimtih 0.This turns off the setting that forces the dimension text to be horizontal. Next type Dimtad 1.This turns on the text-above-dimension feature. You’ll want these two settings on to match the appearance of text in the metric ISO-25 style. Again, metric users do not have to change these settings.
Now you are ready to start drawing the window.
Dimensioning Nonorthogonal Linear Distances
Now you will dimension the window. The unusual shape of the window prevents you from using the horizontal or vertical dimensions you’ve used already. However, the Dimension > Aligned option will allow you to dimension at an angle.
- Click the Aligned Dimension tool on the Dimension toolbar. You can also enter Dal to start the aligned dimension or select Dimension > Aligned.
- At the Specify first extension line origin or <select object>:
prompt, press button You could have picked extension line origins as you did in earlier examples, but using the shows you first hand how the Select option works.
- At theSelect object to dimension: prompt, pick the upper-right face of the hexagon near coordinate 2′-5″,1′-10″ (75,55 for metric users). As the prompt indicates, you can also pick an arc or circle for this type of dimension.
- At the specify dimension line location or [Mtext/Text/Angle]:
prompt, pick a point near coordinate 34,26 (90,60 for metric users). The dimension appears in the drawing as shown in Figure 9.13.
Next, you will dimension a face of the hexagon. Instead of its actual length, however, you will dimension a distance at a specified angle-the distance from the center of the face.
- Click the Linear Dimension tool on the Dimension toolbar.
- At the Specify first extension line origin or <select> object:
prompt, press button.
- At the Select object to dimension: prompt, pick the lower-right face of the hexagon near coordinate 30,16 (77,:31 for metric users).
- At the Specify dimension line location
- At the Dimension line angle <0>: prompt,enter 30 button.
- At the Dimension line location: prompt, pick a point near coordinate 35,8 (88,12 for metric users). Your drawing will look like Figure 9.14.
Dimensioning Radii, Diameters, and Arcs
To dimension circular objects, you use another set of options from the Draw > Dimensioning menu.
- Click Angular Dimension on the Dimension toolbar. Or you can enter Dan or choose Dimension > Angular from the pull-down menu to start the angular dimension. .
- At the Select second line: prompt, pick the top face at coordinate 21,26 54,62 for metric users).
- At the Specify dimension arc line location or [Mtext/Text/Angle]: prompt, notice that as you move the cursor around the upper-left comer of the hexagon, the dimension changes, as shown in the top images of Figure 9.15.
- Pick a point near coordinate 21,23 (49,50 for metric users). The dimension is fixed in the drawing (see the bottom image of Figure 9.15).
Now try the Diameter option, which shows the diameter of a circle.
- Click the Diameter Dimension tool on the Dimension toolbar. Or you can enter Ddi at the command prompt.
- At the Select arc or circle: prompt, pick the circle.
- At the Specify dimension line location or [Mtext/Text/Angle]:
prompt, you will see the diameter dimension drag along the circle as you move the cursor. If you move the cursor outside the circle, the dimension will change to display the dimension on the outside (see the top image of Figure 9.16).
- Place the cursor inside the circle so that the dimension arrow points in a horizontal direction, as shown in the bottom image of Figure 9.16.
- With the text centered, click the mouse.
The Radius Dimension tool on the Dimension toolbar gives you a radius dimension just as the diameter dimension provides a circle’s diameter.
Figure 9.17 shows a radius dimension on the outside of the circle, but you can place it inside in a manner similar to the diameter dimension. The Center Mark tool on the Dimension toolbar just places a cross mark in the center of the selected arc or circle.