AutoCAD 2005 For Dummies (2004)

scale, sheet size, and other desired properties of the drawing. You can set some system variables in AutoCAD dialog boxes, but a few require that you type at the command line. Table 3-3 shows the settings that you most commonly need to change — or at least check — during drawing setup, along with the names of the corresponding system variables. Later in the chapter, in the section “The Main Course: Model Space,” I show you the procedure for changing these settings.

Getting Creative with Templates

When you start AutoCAD 2004 with its desktop shortcut or from the Windows Start menu, AutoCAD creates a new, blank drawing based on the default template drawing (Acad.dwt). When you explicitly create a new drawing from within AutoCAD, the Select Template dialog box, shown in Figure 3-4, appears by default so that you can choose a template on which to base your new drawing.

A template is simply a drawing whose name ends in the letters DWT, which you use as the starting point for another drawing. When you create a new drawing from a template, AutoCAD makes a copy of the template file and opens the copy in a new drawing editor window. The first time you save the file, you’re prompted for a new filename to save to; the original template file stays unchanged.

You may be familiar with the Microsoft Word or Excel template documents, and AutoCAD template drawings work pretty much the same way — because Autodesk stole the idea from them! (Encouraged, of course, by Microsoft.)

2.Click the name of the template that you want to use as the starting point for your new drawing.

3.Click the Open button.

A new drawing window with a temporary name, such as Drawing2.dwg, appears. (The template you opened remains unchanged on your hard disk.)

Depending on which template you choose, your new drawing may open with a paper space layout tab, not the Model tab, selected. If that’s the case, click the Model tab before changing the settings described in “The Main Course: Model Space.” The section “Plot Layouts for Any Palate,” later in this chapter, describes how to set up and take advantage of paper space layouts.

4.Press Ctrl+S and save the file under a new name.

Take the time to save the drawing to the appropriate name and location now.

5.Make needed changes.

For most of the templates that come with AutoCAD, you need to consider changing the units, limits, grid and snap settings, linetype scale, and dimension scale. See the section, “The Main Course: Model Space,” for instructions.

6.Consider saving the file as a template.

If you’ll need other drawings in the future similar to the current one, consider saving your modified template as a template in its own right. See the section “Cooking Up Terrific Templates” later in this chapter.

The simplest, no-frills templates are Acad.dwt (for people who customarily work with sheet sizes expressed in inches) and Acadiso.dwt (for people who customarily work with sheet sizes expressed in millimeters). Most of the remaining templates that come with AutoCAD include title blocks for various sizes of sheets. In addition, most templates come in two versions — one for people who use color-dependent plot styles and one for people who use named plot styles. You probably want the colordependent versions. (Chapter 12 describes the two kinds of plot styles and why you probably want the color-dependent variety.) I warned you that this drawing setup stuff would be complicated!

If you dig around in the Options dialog box, you may discover a setting that turns on the old Startup dialog box, which offers several options other than starting with a template. Among these options are the enticingly named Setup Wizards. These so-called wizards were lame when they first appeared; they’re no better now. Autodesk acknowledges as much by making them almost impossible to find in AutoCAD 2005.

AutoCAD can think in inches! If you’re using Engineering or Architectural units (feet and inches), AutoCAD understands any coordinate you enter as a number of inches. You use the ’ (apostrophe) character on your keyboard to indicate a number in feet instead of inches.

3.From the Length Precision drop-down list, choose the degree of precision you want when AutoCAD displays coordinates and linear measurements.

The precision setting controls how precisely AutoCAD displays coordinates, distances, and prompts in some dialog boxes. In particular, the Coordinates box on the status bar displays the current cursor coordinates using the current precision. A grosser — that is, less precise — precision setting makes the numbers displayed in the status bar more readable and less jumpy. So be gross for now; you can always act a little less gross later.

The linear and angular precision settings only affect AutoCAD’s display of coordinates, distances, and angles on the status bar, in dialog boxes, and in the command line area. For drawings stored as DWG files, AutoCAD always uses maximum precision to store the locations and sizes of all objects that you draw. In addition, AutoCAD provides separate settings for controlling the precision of dimension text — see Chapter 10 for details.

4.Choose an angular unit type from the Angle Type drop-down list.

Decimal Degrees and Deg/Min/Sec are the most common choices.

The Clockwise check box and the Direction button provide additional angle measurement options, but you’ll rarely need to change the default settings: Measure angles counterclockwise and use east as the 0 degree direction.

5.From the Angle Precision drop-down list, choose the degree of precision you want when AutoCAD displays angular measurements.

6.In the Drag-and-Drop Scale area, choose the units of measurement for this drawing.

Choose your base unit for this drawing — that is, the real-world distance represented by one AutoCAD unit.

7.Click OK to exit the dialog box and save your settings.

Telling your drawing its limits

The next model space setup task is to set your drawing’s limits. You wouldn’t want it staying out all night and hanging out with just anybody, would you? The limits represent the rectangular working area that you’ll draw on, which usually corresponds to the paper size. Setting limits correctly gives you the following advantages:

The initial units offered by AutoCAD correspond to an architectural A size sheet of paper in landscape orientation. (Almost no one uses Architectural A size paper; here’s a classic example of a programmer choosing a silly default that no one has bothered to change in 22 years!)

3.Type the upper-right corner of the limits you want to use and press Enter.

You calculate the usual setting for the limits upper-right corner by multiplying the paper dimensions by the drawing scale factor. For example, if you’re setting up a 1⁄8” = 1’–0” drawing (drawing scale factor = 96) to be plotted on a 24-x-36-inch sheet in landscape orientation, the upper-right corner of the limits should be 36 inches times 96, 24 inches times 96. Okay, pencils down. The correct answer is 3456,2304 (or 288 feet,192 feet).

Alternatively, you can cheat when specifying limits and read the limits from the tables on the Cheat Sheet.

If you have the grid turned on, AutoCAD redisplays it in the new limits area after you press Enter.

If you’re using Architectural or Engineering units and you want to enter measurements in feet and not inches, you must add the foot designator after the number, such as 6’; otherwise, AutoCAD assumes that you mean inches.

4.Choose View Zoom All.

AutoCAD zooms to the new limits.

Making the drawing area snap-py (and grid-dy)

AutoCAD’s grid is a set of evenly spaced, visible dots that serve as a visual distance reference. (As I describe in “Telling your drawing its limits,” earlier in this section, the grid also indicates how far the drawing limits extend.) AutoCAD’s snap feature creates a set of evenly spaced, invisible hot spots, which makes the cursor move in nice, even increments. Both grid and snap are like the intersection points of the lines on a piece of grid paper, but grid is simply a visual reference, whereas snap constrains the points that you can pick with the mouse. You can — and usually will — set the grid and snap spacing to different distances.

Set the grid and the snap intervals in the Drafting Settings dialog box with these steps:

1.Right-click the Snap or Grid button in the status bar and choose Settings.

The Drafting Settings dialog box appears with the Snap and Grid tab selected, as shown in Figure 3-6.