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The system variable MEASUREMENT can be used to override the default for a specific drawing, but it affects only text, hatching, and noncontinuous line types.

Let’s get stylish!

The following steps describe how to create your own dimension style(s):

1.On the Ribbon’s Home tab, click the label of the Annotation panel to open the panel slideout, and then click the Dimension Style button.

Alternatively, if that just sounds like too much work, you could type D and press Enter. The Dimension Style Manager dialog box appears.

2.In the Styles list, select the existing dimension style whose settings you want to use as the starting point for the settings of your new style.

For example, select the default dimension style named Standard or ISO-25.

3.Click the New button to create a new dimension style that’s a copy of the existing style.

The Create New Dimension Style dialog box appears.

4.Enter a New Style Name and then select or deselect the Annotative check box. Click Continue.

Select the Annotative check box to create an annotative dimension style, or deselect it for a non-annotative style. Refer to Chapter 13 and later in this chapter for more about annotative objects.

The New Dimension Style dialog box appears. (This dialog box is virtually identical to the Modify Dimension Style dialog box.)

5.Modify dimension settings on any of the seven tabs in the New Dimension Style dialog box.

See the descriptions of these settings in the next section of this chapter.

6.Click OK to close the New Dimension Style dialog box.

The Dimension Style Manager dialog box reappears.

7.Click Close.

The Dimension Style Manager dialog box closes, and your new dimension style becomes the current dimension style that AutoCAD uses for future dimensions in this drawing.

8.Draw some dimensions to test your new dimension style.

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312 Part III: If Drawings Could Talk

Avoid changing existing dimension styles that you didn’t create unless you know for sure what they’re used for. When you change a dimension style setting, all existing dimensions that use that style change to reflect the revised setting. Thus, one small dimension variable setting change can affect a large number of existing dimensions! To play it safe, instead of modifying an existing dimension style, create a new style by copying an existing one and modifying the new one.

A further variation on the already convoluted dimension styles picture is that you can create dimension substyles (also called style families), which are variations of a main style that affect only a particular type of dimension, such as radial or angular. If you open the Dimension Style Manager dialog box and see names of dimension types indented beneath the main dimension style names, be aware that you’re dealing with substyles.

Adjusting style settings

After you click New or Modify in the Dimension Style Manager dialog box, AutoCAD displays a tabbed New Dimension Style or Modify Dimension Style dialog box (the two dialog boxes are identical except for the title bar) with a mind-boggling — and potentially drawing-boggling, if you’re not careful — array of settings.

Fortunately, the dimension preview that appears on all tabs — as well as on the main Dimension Style Manager dialog box — immediately shows the results of most setting changes. With the dimension preview and some trial- and-error changing of settings, you can usually home in on an acceptable group of settings. For more information, use the dialog box help feature: Just hover your mouse pointer over the setting that you want to know more about.

Before you start messing with dimension style settings, it’s important to know what you want your dimensions to look like when they’re plotted. If you’re not sure how it’s done in your industry, ask others in your office or profession, or look at a plotted drawing that someone in the know represents as being a good example. A general rule we’ve found to be helpful in virtually all aspects of life is to stick with the defaults unless you know specifically what you want to change — and why.

The following sections introduce you to the more important tabs in the New/ Modify Dimension Style dialog boxes and highlight useful settings. Note that whenever you specify a distance or length setting, you should enter the desired plotted size. We discuss plotting size scale factors in Chapters 13 (text) and 15 (hatching), and later in this chapter.

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Chapter 14: Entering New Dimensions 313

Following lines and arrows

The settings on the Lines tab and the Symbols and Arrows tab control the basic look and feel of all parts of your dimensions, except text.

Symbolically speaking

The settings on the Symbols and Arrows tab control the shape and appearance of arrowheads and other symbols.

A useful setting is Center Marks. Depending on which radio button you select, placing a radius or diameter dimension will also identify the center by placing a small center mark, or center lines that extend just beyond the circle or arc, or none. The default is tick marks, but we prefer lines because normal drafting practice is usually to show center lines.

Tabbing to text

Use the Text tab to control how your dimension text looks — the text style and height to use (see Chapter 13) and where to place the text with respect to the dimension and extension lines. In particular, note the Text Style dropdown, which contains a list of the text styles available in the drawing. The three-dot button at the right end of the list gives direct access to the text style dialog box so you can edit or create a suitable text style if one doesn’t already exist in your current drawing. See Chapter 13 for more information on text styles. The default Text Height in imperial units is too large for most situations — set it to 1/8", 3mm, or another height that makes sense.

Even if you’re opposed to defacing books, get out a bright red marker and put a circle around this warning, even if you borrowed the book from the library or a friend. Here goes: You must define the text style that you specify for a dimension style with a height of 0 (zero) in the Text Style dialog box. (See Chapter 13 for more information about variable-height and fixed-height text styles.) If you specify a fixed-height text style for a dimension style, the text style’s height will override the Text Height setting in the New/Modify Dimension Style dialog boxes. Use a zero-height style to avoid the problem — and bear in mind that using nonzero-height text styles in dimensions is one of the most common mistakes made by new AutoCAD users.

Getting fit

The Fit tab includes a bunch of options that control when and where AutoCAD shoves the dimension text if it doesn’t quite fit between the extension lines. The default settings leave AutoCAD in “maximum attempt at being helpful” mode — that is, AutoCAD moves the text, dimension lines, and arrows around automatically so that things don’t overlap. On rare occasions, AutoCAD’s guesses might be less than perfect. It’s usually easier to adjust the

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314 Part III: If Drawings Could Talk

text placement by grip editing the placed dimension, as we describe in the section “Editing dimension geometry,” later in this chapter, instead of messing with dimension style settings.

Even at its most helpful, AutoCAD sometimes makes a bad first guess about how you want your dimension text and arrows arranged. If you’re having problems getting the look you want, don’t flip your wig — flip your arrows to the other side of the dimension lines by selecting the dimension and choosing Flip Arrow from the multifunction grip on the arrow.

Most important, the Fit tab includes the Annotative check box. Using annotative dimensions, as we recommend in this chapter, will make your dimensioning go a lot more smoothly!

We highly recommend that you get comfortable with annotative dimensioning in model space. Unfortunately, old-style (that is, non-annotative) dimensioning is still part of the program, and many offices will probably keep doing it that way for a while to come.

The Use Overall Scale Of setting corresponds to the DIMSCALE system variable, and you’ll hear long-time AutoCAD drafters refer to it as such. In Chapters 13 (text) and 15 (hatching), we refer to a scale factor by which text height and hatch patterns need to be multiplied so they plot properly. This also applies to dimensions. If you are using old-style non-annotative dimensions, this is where that number goes. It resizes text height, arrowhead sizes, and gaps accordingly. When Scale Dimensions to Layout (for paper space layout dimensioning) is selected, DIMSCALE is automatically set to 0 (zero). When Annotative is selected, DIMSCALE is ignored, and a suitable scale factor is applied to each dimension when it’s created.

Using primary units

The Primary Units tab gives you highly detailed control over how AutoCAD formats the characters in the dimension text string. You usually want to set the Unit format and Precision and maybe specify a suffix for unitless numbers if it’s not clear from your drawing what units you’re using. You may also change the Zero Suppression settings, depending on whether you want dimension text to read 0.5000, .5000, or 0.5. (“Zero Suppression!” also makes a great rallying cry for organizing your fellow AutoCAD drafters.)

AutoCAD 2010 introduced an interesting tweak to dimension text: Dimension subunits. If the main unit of measure on your drawing is meters — rather than have a bunch of smaller distances dimensioned as, say, 0.450 — you could create a centimeter subunit so that any dimension of less than 1 meter would be shown in centimeters. We were always taught a very strict drafting standard that says that all dimensions on a drawing must be in the same units. In other words, in a drawing with meters as the dimension unit, 0.45 would

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