Bonus Appendix D

System Variables and Dimension Styles

AutoCAD is a complex program with a vast set of options and settings. You don’t need to know everything about AutoCAD to be a productive user, but it does help to be aware of some of the inner workings that let you fine-tune the program.

This appendix covers a few of the details that can help you get tighter control over the way AutoCAD works. You’ll find a brief discussion of system variables that give you direct control over options and features. That discussion is followed by a detailed look at dimension styles settings.

System Variables

System variables let you fine-tune your AutoCAD environment. Most of the system variables control the same options you find in AutoCAD’s dialog boxes and palettes. The main advantage of system variables is that you can set them without having to dig through a series of dialog boxes.

To set a system variable, you enter the variable name at the Command prompt. Or, if you’re in the middle of another command, you can set a system variable by entering the variable name preceded by an apostrophe. For example, if you’re drawing a series of line segments, you can enter ´Snapang↵ at the Specify next point or [Undo]: prompt to change the Snapang system variable on the fly.

Because system variables are command-line driven and don’t require access to a dialog box, you can use them in your custom macros to control settings. You can also access system variables through AutoLISP by using the Getvar and Setvar functions.

A list of the system variables and their functions could take up a full chapter. A detailed look at system variables is beyond the scope of this book, but you have an excellent resource for information about system variables in the AutoCAD for Mac Help website. Choose Help ⇒ AutoCAD Help from the menu bar. When your browser opens to the Help website, click the Command Reference option in the left panel and then click System Variables just to the right of the list. You see the system variables listed in alphabetical order.

You can also find system variables through the features and commands they control. For example, if you search for Grip in the AutoCAD for Mac Help website, you’ll see Use Grip Modes at the top of a list. Click this option and a page describing the grip modes is displayed. Scroll to the bottom of the page and click the System Variables option. The system variables related to the grip mode are displayed (see Figure D-1). You can click on a system variable name to get more detailed information.

Taking a Closer Look at the Dimension Style Dialog Boxes

As you saw in Chapter 11, “Using Dimensions,” you can control the appearance and format of dimensions through dimension styles. You can create new dimension styles or edit existing ones. The following sections describe all the components of the dialog boxes you use to create and maintain dimension styles.

The Dimension Style Manager

The Dimension Style Manager is the gateway to dimension styles. With this dialog box, you can create a new dimension style, edit existing dimension styles, or make an existing dimension style current. To open the Dimension Style Manager (see Figure D-2), choose Format ⇒ Dimension Style from the menu bar or type Dimstyle↵.

The following sections describe the options in the Dimension Style Manager.

Preview Of

The image in the right half of the Dimension Style Manager gives you a preview of your dimension style. It shows a sample of most of the types of dimensions you’ll use, formatted the way you specified when you created or modified your dimension style.

Description

The Description box displays a description for the selected dimension style. When you create or modify a dimension style, you have the option to create or edit the dimension style description.

The Styles List Box

The Styles list box displays the available dimension styles. You can highlight the dimension style names in the Styles list box to indicate a style to be used with the Set Current, New, Modify, and Override options. You can also right-click a style name and make it current, rename it, or delete the selected style.

The List Pop-up Menu

The List pop-up menu lets you control what is listed in the Styles list box. You can display either all the styles available or only the styles in use in the drawing.

Don’t List Styles in Xrefs

The Don’t List Styles In Xrefs check box lets you specify whether dimension styles in Xrefs are listed in the Styles list box. This option is grayed out if no Xrefs are present in the current drawing.

The Set Current Right-Click Option

The Set Current right-click option lets you set the dimension style highlighted in the Styles list box to be current. To view this option, select a style from the list and right-click.

The Add and Delete Buttons

The Add button, which looks like a plus sign, lets you create a new dimension style. It uses the dimension style that is highlighted in the Styles list box as the basis for the new style. The Delete button, which looks like a minus sign, deletes the highlighted dimension style.

Clicking the Add button opens the Create New Dimension Style dialog box.

In the Create New Dimension Style dialog box, you can enter the name for your new dimension style. You can also select the source dimension style on which your new dimension style will be based.

New Style Name Lets you specify the name for your new dimension style.

Start With Lets you select an existing style on which to base your new dimension style.

Annotative Lets you turn on the Annotation Scale feature for the style you are creating. See Chapter 9, “Adding Text to Drawings,” for more on the Annotative Scale feature.

Use For Lets you choose a dimension type for your new dimension style. For a completely new dimension style, use the All Dimensions option in the Use For pop-up menu. If you want to modify the specifications for a particular dimension type of an existing dimension style, select a dimension type from this list. Your modified dimension type will appear in the Styles list box under the main style you specify in the Start With pop-up menu. After you’ve modified a dimension type, the new type will be applied to any new dimensions.

After you’ve entered your options in the Create New Dimension Style dialog box, click Continue. You see the New Dimension Style dialog box described later. When you’re finished setting up your new style, it’s listed in the Styles list box.

The Modify Action Menu

The Modify action menu, which looks like a gear, lets you modify the dimension style that is selected in the Styles list box. Clicking this icon offers several options, including Set Current, Modify, Override, Compare, and Rename. See the next section, “The New/Modify/Override Dimension Style Dialog Box,” for information on the Modify option.

The Override Option The Override option lets you create a temporary dimension style based on an existing style. You may want to use this option if you need to create a dimension that differs only slightly from an existing style.

To use the Override option, select a style from the Styles list box, and then click the Modify action menu and select Override. You’ll see the Override Current Style dialog box, which works like the New or Modify Dimension Style dialog box described later. After you create an override, it’s listed as <style overrides> in the Styles list box, right under the style you used to create the override.

The override then becomes the default dimension style until you select another one from the Styles list box. When you select a different style to be current, a message tells you that the unsaved style will be discarded. To save an override style, select the override from the Styles list box and click New. Then click Continue in the Create New Dimension Style dialog box, and click OK in the New Dimension Style dialog box. You can also merge the override style with its source style by right-clicking <style overrides> and selecting Save To Current Style.

The Compare Option The Compare option lets you compare the differences between two dimension styles. When you click the Modify button and select Compare, the Compare Dimension Styles dialog box opens (see Figure D-3).

You can select the two styles you want to compare from the Compare and With pop-up menus. The differences appear in the list box. Just above the upper-right corner of the list box is a Copy button; this copies the contents of the list box to the Clipboard, enabling you to save the comparison to a word processing document.

The New/Modify/Override Dimension Style Dialog Box

When you click the New button in the Dimension Style Manager and then click Continue in the Create New Dimension Style dialog box, the New Dimension Style dialog box opens.

You’ll also see this same dialog box under a different name when you click the Modify or Override options from the Modify button in the Dimension Style Manager. Clicking Modify brings up the Modify Dimension Style dialog box and clicking Override brings up the Override Current Style dialog box. The options in these dialog boxes let you determine all the characteristics of your dimension style. The following sections provide detailed descriptions of each available option.

The equivalent dimension style variables are shown in brackets at the end of the description of each option.

The Lines Tab

The options in this tab (see Figure D-4) give you control over the appearance of dimension and extension lines. Figure D-5 shows an example of some of the dimension components that are affected by these options. The values you enter here for distances should be in final print sizes and will be multiplied by the dimension scale value in the Fit tab to derive the actual extension distance in the drawing.

The Dimension Lines Group

The following options let you control the general behavior and characteristics of the dimension lines:

Color Lets you set the color of the dimension line. [Dimclrd]

Linetype Lets you set the linetype for dimension lines. [Dimltype]

Lineweight Lets you set the line weight for dimension lines. [Dimlwd]

Extend Beyond Ticks Lets you set the distance that the dimension line extends beyond the extension lines. [Dimdle]

Baseline Spacing Lets you specify the distance between stacked dimensions. [Dimdli]

Suppress Check boxes let you suppress the dimension line on either side of the dimension text. [Dimsd1, Dimsd2]

The Extension Lines Group

The following options let you control the general behavior and characteristics of the extension lines:

Color Lets you set the color for extension lines. [Dimclre]

Linetype Ext Line 1 Controls the linetype for the first extension line. [Dimltex1]

Linetype Ext Line 2 Controls the linetype for the second extension line. [Dimltex2]

Lineweight Lets you set the line weight for extension lines. [Dimlwe]

Suppress Check boxes let you suppress one or both extension lines. [Dimse1, Dimse2]

The Position and Length Group

Extend Beyond Dim Lines Lets you set the distance that extension lines extend beyond dimension lines. [Dimexe]

Offset From Origin Lets you set the distance from the extension line to the object being dimensioned. [Dimexo]

Fixed Length Extension Lines Lets you set the extension lines to a fixed length. The Length input box provides a space to enter the length you want. [Dimfxlon, Dimfxl]

The Symbols and Arrows Tab

The options in this tab give you control over the appearance of arrowheads and center marks (see Figure D-6). The values you enter in this tab for distances should be in final print sizes and will be multiplied by the dimension scale value in the Fit tab to derive the actual extension distance in the drawing.

Arrowheads

The following options let you select the type and sizes of arrowheads for dimensions and leaders:

First Lets you select the type of arrowhead to use on dimension lines. By default, the second arrowhead automatically changes to match the arrowhead you specify for this setting. [Dimblk1]

Second Lets you select a different arrowhead from the one you select for First. [Dimblk2]

Leader Lets you specify an arrowhead for leader notes. [Dimldrblk]

Arrow Size Lets you specify the size for the arrowheads. [Dimasz]

The Center Marks Group

The following options let you set the center mark for radius and diameter dimensions:

None/Mark/Line Lets you select the type of center mark used in radius and diameter dimensions. The Mark option draws a small cross mark, Line draws a cross mark and center lines, and None draws nothing. [Dimcen]

Size input box Lets you specify the size of the center mark. [Dimcen]

The Arc Length Symbol Group

This set of radio buttons controls the display of the arc-length symbol in arc-length dimensions:

Preceding Dimension Text Places the symbol before the dimension text. [Dimarcsym]

Above Dimension Text Places the symbol above the dimension text. [Dimarcsym]

None No symbol. [Dimarcsym]

The Radius Jog Dimension Group

You can set the angle of the radius-dimension jog with this setting. The radius-dimension jog is the short line in the radius dimension that indicates that the dimension is measured to a point out of view. [Dimjogang]

The Linear Jog Dimension Group

You can set the size of the linear-dimension jog with this setting. The linear-dimension jog is the zigzag line that indicates a break in the dimension line.

The Text Tab

The options in the Text tab (see Figure D-7) give you control over the appearance of the dimension text. You can set the text style and default location of text in relation to the dimension line. If the text style you select for your dimension text has a height value of 0, you can set the text height from this tab.

The Appearance Group

The following options give you control over the appearance of text:

Text Style Lets you select an existing text style for your dimension text. You can also create a new style for your dimension text by clicking the Browse button. [Dimtxsty]

Text Color Lets you select a color for your dimension text. [Dimclrt]

Fill Color Lets you select a color for your dimension background. [Dimtfill, Dimtfillclr]

Text Height Lets you specify a text height for dimension text. This option is valid only for text styles with 0 height. [Dimtxt]

Fraction Height Scale Lets you specify a scale factor for the height of fractional text. This option is available only when Architectural or Fractional is selected in the Primary Units tab. [Dimtfac]

Show Text Frame When this option is selected, it draws a rectangle around the dimension text. [Dimgap]

The Placement Group

The following options give you control over the placement of text, including the ability to specify the distance of text from the dimension line:

Vertical Lets you set the vertical position of the text in relation to the dimension line. The options are Centered, Above, Outside, and JIS. Centered places the text in line with the dimension line; the dimension line is broken to accommodate the text. Above places the text above the dimension line, leaving the dimension line unbroken. Outside places the text away from the dimension line at a location farthest from the object being dimensioned. JIS places the text in conformance with the Japanese Industrial Standards. [Dimtad]

Horizontal Lets you set the location of the text in relation to the extension lines. The options are Centered, At Ext Line 1, At Ext Line 2, Over Ext Line 1, and Over Ext Line 2. Centered places the text between the two extension lines. At Ext Line 1 places the text next to the first extension line but still between the two extension lines. At Ext Line 2 places the text next to the second extension line but still between the two extension lines. Over Ext Line 1 places the text above and aligned with the first extension line. Over Ext Line 2 places the text above and aligned with the second extension line. [Dimjust]

View Direction Lets you set the direction of dimension text. The default is Left-to-Right, but you can also set it to Right-to-Left. [Dtxtdirection]

Offset From Dim Line Lets you determine the distance from the baseline of text to the dimension line when text is placed above the dimension line. It also lets you set the size of the gap between the dimension text and the endpoint of the dimension line when the text is in line with the dimension line. You can use this option to set the margin around the text when the dimension text is in a centered position that breaks the dimension line into two segments. [Dimgap]

The Alignment Group

The following options give you control over the alignment of text in relation to the dimension line:

Horizontal Keeps the text in a horizontal orientation regardless of the dimension line orientation. [Dimtih, Dimtoh]

Aligned With Dimension Line Aligns the text with the dimension line. [Dimtih, Dimtoh]

ISO Standard Aligns the text with the dimension line when it’s between the extension lines; otherwise the text is oriented horizontally. [Dimtih, Dimtoh]

The Fit Tab

The options in the Fit tab (see Figure D-8) let you fine-tune the behavior of the dimension text and arrows under special conditions. For example, you can select an optional placement for text and arrows when there isn’t enough room for them between the extension lines.

The Fit Options Group

The Fit Options radio buttons let you determine which dimension component is moved when there isn’t enough room between the extension lines for either the text or the arrows or both:

Either Text Or Arrows (Best Fit) Automatically determines whether only text, only arrows, or both text and arrows will fit between the extension lines, and then places them accordingly. For example, if there isn’t enough room for both text and arrows and the text is wider than the two arrows combined, the text is placed outside the extension lines. If the width of the arrows is greater than the width of the text, the arrows are moved outside the extension lines. If the gap between the extension lines is too narrow for either the text or arrows, both the arrows and the text are moved outside the extension lines. [Dimatfit]

Arrows Moves the arrows outside the extension lines when there isn’t enough room for both arrows and text between the extension lines. If the gap between the extension lines is too narrow for either the text or the arrows, both the arrows and the text are moved outside the extension lines. [Dimatfit]

Text Moves the text outside the extension lines when there isn’t enough room for both arrows and text between the extension lines. If the gap between the extension lines is too narrow for either the text or the arrows, both the arrows and the text are moved outside the extension lines. [Dimatfit]

Both Text And Arrows Moves both the text and the arrows outside the extension lines when there isn’t enough room for both arrows and text between the extension lines. [Dimatfit]

Always Keep Text Between Ext Lines Places the text between the extension lines regardless of whether it fits there. [Dimtix]

Suppress Arrows If They Don’t Fit Inside Extension Lines Removes the arrows entirely if they don’t fit between the extension lines. [Dimsoxd]

The Text Placement Group

The Text Placement radio buttons determine how the dimension text behaves when it’s moved from its default location:

Beside The Dimension Line Keeps the text in its normal location relative to the dimension line. [Dimtmove]

Over Dimension Line, With Leader Lets you move the dimension text independent of the dimension line. A leader is added between the dimension line and the text. [Dimtmove]

Over Dimension Line, Without Leader Lets you move the dimension text independent of the dimension line. No leader is added. [Dimtmove]

The Scale for Dimension Features Group

These options offer control over the scale of the dimension components. You can set a fixed scale, or you can allow the dimension components to be scaled depending on the Paper Space viewport in which they’re displayed:

Annotative Turns on the Annotative Scale feature, which lets you quickly set the size of text to correspond with your drawing’s annotation or viewport scale setting.

Scale Dimensions To Layout Scales all the dimension components to the scale factor assigned to the Paper Space viewport in which the drawing appears. [Dimscale]

Use Overall Scale Of Lets you determine the scale of the dimension components. All the settings in the Dimension Style dialog box are scaled to the value you set in the input box if this radio button is selected. [Dimscale]

The Fine Tuning Group

The following two check boxes offer miscellaneous settings for dimension text and dimension lines:

Place Text Manually Enables you to manually place the dimension text horizontally along the dimension line when you’re inserting dimensions in your drawing. [Dimupt]

Draw Dim Line Between Ext Lines Forces AutoCAD to draw a dimension line between the extension lines no matter how narrow the distance is between them. [Dimtofl]

The Primary Units Tab

The options in the Primary Units tab (see Figure D-9) let you set the format and content of the dimension text, including the unit style for linear and angular dimensions.

The Linear Dimensions Group

The following options give you control over the unit style and the formatting of dimension text for linear dimensions:

Unit Format Lets you determine the unit style of the dimension text. The options are Scientific, Decimal, Engineering, Architectural, Fractional, and System Format. You must set this option independent of the overall drawing units setting (choose Format ⇒ Units from the menu bar) if you want the dimension text to appear in the appropriate style. [Dimunit]

Precision Lets you set the precision of the dimension text. This option rounds off the dimension text to the nearest precision value you set. It doesn’t affect the actual precision of the drawing. [Dimdec]

Fraction Format Available only for Architectural and Fractional unit formats. This option lets you select between vertically stacked, diagonally stacked, and horizontal fractions. [Dimfrac]

Decimal Separator Lets you select a decimal separator for dimension unit formats that display decimals. You can choose a period, a comma, or a space. If you want to use a dimension separator not included in the list, you can use the Dimsep system variable to specify a custom dimension separator. [Dimsep]

Round Off Lets you determine the degree of rounding applied to dimensions. For example, you can set this option to 0.25 to round off dimensions to the nearest 0.25, or ¼, of a unit. [Dimrnd]

Prefix Lets you include a prefix for all linear-dimension text. For example, if you want all your linear dimension text to be preceded by the word Approximately, you can enter Approximately in this input box. Control codes can be used for special characters. See Chapter 9 for more information on character codes. [Dimpost]

Suffix Lets you include a suffix for all linear-dimension text. Control codes can be used for special characters. See Chapter 9 for more information on character codes. [Dimpost]

Scale Factor Lets you set a scale factor for the dimension text. This option scales the value of the dimension text to the value you enter. For example, if you want your dimensions to display distances in centimeters even though the drawing was created in inches, you can enter 2.54 for this option. Your dimension text will then display dimensions in centimeters. Conversely, if you want your dimension text to show dimensions in inches even though you’ve created your drawing using centimeters, you enter 0.3937 (the inverse of 2.54) for this option. [Dimlfac]

Apply To Layout Dimensions Only Causes AutoCAD to apply the measurement scale factor to Paper Space layouts only. With this check box selected, the Dimlfac dimension variable gives a negative value. [Dimlfac]

The Zero Suppression Group

This group lets you suppress zeros so they don’t appear in the dimension text.

Leading, Trailing, 0 Feet, and 0 Units For dimensions other than architectural, you can suppress leading and trailing zeros. For example, 0.500 becomes .500 if you suppress leading zeros. It becomes 0.5 if you suppress trailing zeros. For architectural dimensions, you can suppress zero feet or zero inches, although typically you wouldn’t suppress zero inches [Dimzin]. The 0 feet and 0 inches options are grayed out until you select the Leading or Trailing options and you have Architectural selected as the length style in the Drawing Units dialog box (Format ⇒ Units).

Sub-Units Factor Lets you control the number of places for numbers to the right of the decimal point. This is helpful if you are working in metric measurements.

Sub-Unit Suffix Allows you to add a suffix to a dimension. For example, you can enter cm here to display centimeter abbreviation after a sub-unit value.

The Angular Dimensions Group

The following options enable you to format angle dimensions:

Units Format Lets you select a format for angular dimensions. The options are Decimal Degrees, Degrees Minutes Seconds, Gradians, and Radians. [Dimaunit]

Precision Lets you set the precision for the angular dimension text. [Dimadec]

Zero Suppression The check boxes in this group let you suppress leading or trailing zeros in angular dimensions. For example, 0.500 becomes .500 if you suppress leading zeros. It becomes 0.5 if you suppress trailing zeros. [Dimazin]

The Alternate Units Tab

The Alternate Units tab (see Figure D-10) lets you apply a second set of dimension text labels for dimensions. This second set of text labels can be used for alternate dimension styles or units. Typically, alternate units are used to display dimensions in metric if your main dimensions are in feet and inches.

Select the Display Alternate Units check box to turn on alternate units. This causes AutoCAD to include additional dimension text in the format you specify in the Alternate Units tab. [Dimalt]

The Alternate Units Group

The following options offer control over the unit style and the formatting of dimension text for linear dimensions:

Unit Format Lets you determine the unit style of the dimension text. The options are Scientific, Decimal, Engineering, Architectural Stacked, Fractional Stacked, Architectural, Fractional, and System Format. You must set this option independent of the overall drawing units setting (choose Format ⇒ Units from the menu bar) if you want the dimension text to appear in the appropriate style [Dimaltu]. You can adjust the size of fractions relative to the main dimension text by using the Dimfac dimension variable.

Precision Lets you set the precision of the dimension text. This option rounds off the dimension text to the nearest precision value you set. It doesn’t affect the actual precision of the drawing. [Dimaltd]

Multiplier For Alt Units Lets you set a multiplier value for the dimension text. This option multiplies the value of the dimension text by the value you enter. For example, if you want your alternate dimensions to display distances in centimeters even though the drawing was created in inches, you can enter 2.54 for this option. Your alternate dimension text will then display dimensions in centimeters. Conversely, if you want to have your alternate dimension text show dimensions in inches even though you’ve created your drawing by using centimeters, you enter 0.3937 (the inverse of 2.54) for this option. [Dimaltf]

Round Distances To Lets you determine the degree of rounding applied to alternate dimensions. For example, you can set this option to 0.25 to round off dimensions to the nearest 0.25, or ¼˝, of a unit. [Dimaltrnd]

Prefix Lets you include a prefix for all linear alternate dimension text. For example, if you want all linear-dimension text to be preceded by the word Approximately, you can enter Approximately in the Prefix input box. Control codes can be used for special characters. See Chapter 9 for more information on character codes. [Dimpost]

Suffix Lets you include a suffix for all linear alternate dimension text. Control codes can be used for special characters. See Chapter 9 for more information on character codes. [Dimapost]

The Zero Suppression Group

This group lets you suppress zeros so they don’t appear in the alternate dimension text.

Leading, Trailing, 0 Feet, and 0 Units For dimensions other than architectural, you can suppress leading and trailing zeros. For example, 0.500 becomes .500 if you suppress leading zeros. It becomes 0.5 if you suppress trailing zeros. For architectural dimensions, you can suppress zero feet or zero inches, although typically you wouldn’t suppress zero inches. The 0 feet and 0 inches options are grayed out until you select the Leading or Trailing options. [Dimaltz]

Sub-Units Factor Lets you control the number of places for numbers to the right of the decimal point. This is helpful if you are working in metric measurements.

Sub-Unit Suffix Allows you to add a suffix to a dimension. For example, you can enter cm here to display the centimeter abbreviation after a sub-unit value.

The Placement Group

The following options let you determine the location for the alternate units:

After Primary Value Places the alternate dimension text behind and aligned with the primary dimension text. [Dimapost]

Below Primary Value Places the alternate dimension text below the primary dimension text and above the dimension line. [Dimapost]

The Tolerances Tab

The options in the Tolerances tab (see Figure D-11) offer the inclusion and formatting of tolerance dimension text.

The Tolerance Format Group

The following options offer control over the format of tolerance dimension text:

Method Lets you turn on and set the format for the tolerance dimension text. The options are None, Symmetrical, Deviation, Limits, and Basic. None turns off the tolerance dimension text. Symmetrical adds a plus/minus tolerance dimension; this is a single dimension preceded by a plus/minus sign. Deviation adds a stacked tolerance dimension showing separate upper and lower tolerance values. The Limits option replaces the primary dimension with a stacked dimension showing maximum and minimum dimension values. The Basic option draws a box around the primary dimension value. If an alternate dimension is used, the box encloses both primary and alternate dimension text. [Dimtol, Dimlim, (minus) Dimgap]

Precision Lets you set the precision of the tolerance dimension text. This option rounds off the dimension text to the nearest precision value you set. It doesn’t affect the actual precision of the drawing. [Dimtdec]

Upper Value Lets you set the upper tolerance value for the Symmetrical, Deviation, and Limits tolerance methods. [Dimtp]

Lower Value Lets you set the lower tolerance value for the Deviation and Limits tolerance methods. [Dimtm]

Scaling For Height Lets you adjust the size for the tolerance dimension text as a proportion of the primary dimension text height. [Dimtfac]

Vertical Position Lets you determine the vertical position of the tolerance text. The options are Top, Middle, and Bottom. The Top option aligns the top tolerance value of a stacked pair of values with the primary dimension text. Middle aligns the gap between stacked tolerance values with the primary dimension text. Bottom aligns the bottom value of two stacked tolerance values with the primary dimension text. [Dimtolj]

Align These radio buttons set the alignment of stacked tolerance values. The two options, Decimal Separators and Operational Symbols, are self-explanatory.

Suppress These options let you suppress zeros so they don’t appear in the tolerance dimension text. For dimensions other than architectural, you can suppress leading and trailing zeros. For example, 0.500 becomes .500 if you suppress leading zeros. It becomes 0.5 if you suppress trailing zeros. For architectural dimensions, you can suppress zero feet or zero inches, although typically you wouldn’t suppress zero inches [Dimtzin]. The Leading Zeros and Trailing Zeros options are grayed out until you select an option other than None from the Method pop-up list.

The Alternate Unit Tolerance Group

The Precision pop-up menu lets you set the precision of the alternate tolerance dimension text. This option rounds the dimension text to the nearest precision value you set. It doesn’t affect the actual precision of the drawing [Dimalttd]. You can also control zero suppression (see “Suppress” in the preceding section).

Notes on Metric Dimensioning

The AutoCAD user community is worldwide, and many of you may be using the metric system in your work. As long as you aren’t mixing Imperial (feet and inches) and metric measurements, using the metric version of AutoCAD is fairly easy. In the Drawing Units dialog box (choose Format ⇒ Units from the menu bar), set your measurement system to decimal, set the Units To Scale Inserted Content option to the appropriate metric option, and then draw distances in millimeters or centimeters. At output time, select the MM radio button (millimeters) under Paper Size and Paper Units in the Print dialog box.

If your drawings are to be in both Imperial and metric measurements, you’ll be concerned with several settings, as follows:

Dimlfac Sets the scale factor for dimension values. The dimension value will be the measured distance in AutoCAD units times this scale factor. Set Dimlfac to 25.4 if you’ve drawn in inches but want to dimension in millimeters. The default is 1.0000. If you want to scale dimension values from millimeters to inches, use a value of 0.03937.

Dimalt Turns the display of alternate dimensions on or off. Alternate dimensions are made up of dimension text added to your drawing in addition to the standard dimension text.

Dimaltf Sets the scale factor for alternate dimensions (that is, to metric from Imperial). The default is 25.4, which is the millimeter equivalent of 1˝. If you’re using metric ISO units, the default is 0.03937, which is the inch equivalent of 1 mm.

Dimaltd Sets the number of decimal places displayed in the alternate dimensions.

Dimapost Adds a suffix to alternate dimensions, as in 4.5 mm.

If you prefer, you can use the metric template drawing supplied by AutoCAD:

These templates are set up for metric/ISO standard drawings.

Drawing Blocks for Your Own Dimension Arrows and Tick Marks

If you don’t want to use the arrowheads supplied by AutoCAD for your dimension lines, you can create a block of the arrowheads or tick marks you want to be used in the Arrowheads group of the Dimension Styles dialog box.

To access the Arrowhead options, open the Symbols And Arrows tab of the New Dimension Style, Modify Dimension Style, or Override Current Style dialog box.

For example, suppose you want a tick mark that is thicker than the dimension lines and extensions. You can create a block of the tick mark on a layer you assign to a thick pen weight and then assign that block to the Arrowhead setting. To do so, type Dimstyle↵ to open the Dimension Styles Manager; then select a style from the Styles list and click the Modify action button (gear icon) and then click Modify from the pop-up menu. In the Symbols And Arrows tab, select User Arrow from the First pop-up menu in the Arrowheads group. In the Select Custom Arrow Block dialog box, enter the name of your arrow block.

When you draw the arrow block, make it 1 unit long. The block’s insertion point will be used to determine the point of the arrow that meets the extension line, so make sure you place the insertion point at the tip of the arrow. Because the arrow on the right side of the dimension line will be inserted with a zero rotation value, create the arrow block so that it’s pointing to the right (see Figure D-12). The arrow block is rotated 180° for the left side of the dimension line.

If you want a different type of arrow at both ends of the dimension line, create a block for each arrow. In the Symbols And Arrows tab of the Dimension Styles dialog box, choose User Arrow in the pop-up menu for the first arrowhead and enter the name of one block. Then choose User Arrow in the pop-up menu for the second arrowhead and enter the name of the other block.