Before you determine the dimensions of a project, your design is in flux and many questions may be unanswered. After you begin dimensioning, you'll start to see whether things fit or work together. Dimensioning can be crucial to how well a design works and how quickly it develops. The dimensions answer questions about code conformance if you're an architect; they answer questions about tolerances, fit, and interference if you're involved in mechanical applications. After you and your design team reach a design on a schematic level, communicating even tentative dimensions to others on the team can accelerate design development. Dimensions represent a point from which you can develop your ideas further.
With AutoCAD, you can easily add tentative or final dimensions to any drawing. AutoCAD gives you an accurate dimension without your having to take measurements. You pick the two points to be dimensioned and the dimension line location, and AutoCAD does the rest. AutoCAD's associative dimensioning capability automatically updates dimensions whenever the size or shape of the dimensioned object changes. These dimensioning features can save you valuable time and reduce the number of dimensional errors in your drawings.
In this chapter, you'll learn to do the following:
Before you start the exercises in this chapter, it will help to know the names of the parts of a dimension. Figure 12.1 shows a sample of a dimension with the parts labeled. The dimension line is the line that represents the distance being dimensioned. It's the horizontal line with the diagonal tick marks on either end. The extension lines are the lines that originate from the object being dimensioned. They show you the exact location from which the dimension is taken. The dimension text is the dimension value, usually shown inside or above the dimension line.
Another component of a dimension line is the dimension line extension. This is the part of the dimension line that extends beyond the extension line. Dimension line extensions are usually used only on architectural dimensions. The extension lines usually extend beyond the dimension lines in all types of dimensions. The extension line offset from origin is the distance from the beginning of the extension line to the object being dimensioned. The extension beyond dimension line is the distance the dimension line extends past the extension line and is most commonly used in architectural drawings.
You can control each of these components by creating or editing dimension styles. Dimension styles are the settings that determine the look of your dimensions. You can store multiple styles in a single drawing. The first exercise in this chapter will show you how to create a dimension style.
Dimension styles are similar to text styles. They determine the look of your dimensions as well as the size of dimensioning features, such as the dimension text and arrows. You can set up a dimension style to have special types of arrows, for instance, or to position the dimension text above or in line with the dimension line. Dimension styles also make your work easier by enabling you to store and duplicate your most common dimension settings.
AutoCAD gives you one of two default dimension styles, ISO-25 or Standard, depending on whether you use the metric or Imperial (also called English) measurement system. You'll probably add many other styles to suit the types of drawings you're creating. You can also create variations of a general style for those situations that call for only minor changes in the dimension's appearance.
In this section, you'll learn how to set up your own dimension style based on the Standard dimension style (see Figure 12.2). For metric users, the settings are different, but the overall methods are the same.
Follow these steps to create a dimension style:
Open the
Unitfile you edited in the preceding chapter. If you didn't create one, use the12a-unit.dwgfile and rename itUnit.dwg. Metric users should open12a-unit-metric.dwgand rename itUnit.dwg.Choose All from the Zoom flyout in the View tab's Navigate panel or type Z
Select Standard from the Styles list box. Metric users should select ISO-25. See Figure 12.3.
Click New to open the Create New Dimension Style dialog box (Figure 12.4).
With the Copy of Standard or ISO-25 name highlighted in the New Style Name input box, enter My Architectural.
Click Continue to open the detailed New Dimension Style dialog box (Figure 12.5).
You've just created a dimension style called My Architectural, but at this point it's identical to the Standard style on which it's based. Nothing has happened to the Standard style; it's still available if you need to use it.
Now you need to set up your new dimension style so that it conforms to the U.S. architectural style of dimensioning. Let's start by changing the unit style for the dimension text. Just as you changed the overall unit style of AutoCAD to a feet-and-inches style for your bath drawing in Chapter 3, you must change your dimension styles. Setting the overall unit style doesn't automatically set the dimension unit style. Follow these steps:
In the New Dimension Style dialog box, click the Primary Units tab (see Figure 12.6).
In the Linear Dimensions group, open the Unit Format drop-down list and choose Architectural. Notice that this drop-down list contains the same unit styles as the main Drawing Units dialog box (choose Drawing Utilities
Select 0′-0 ¼″ from the Precision drop-down list, just below the Unit Format list. Metric users should select 0.00. The Precision option enables you to set the level of precision that is displayed in the dimension text. It doesn't limit the precision of AutoCAD's drawing database. This value is used to limit only the display of dimension text values.
Just below the Precision drop-down list, open the Fraction Format drop-down list and select Diagonal. Notice what happens to the graphic: the fractional dimensions change to show how your dimension text will look. Metric users can skip this step because it isn't available when the Decimal unit format is selected.
In the Zero Suppression group in the lower-left corner, click 0 Inches to deselect this check box. If you leave it turned on, indications of 0 inches will be omitted from the dimension text. (In architectural drawings, 0 inches are shown as in this dimension: 12′-0″.) Metric users can ignore this option.
If you use the Imperial measurement system, you've set up My Architectural's dimension unit style to show dimensions in feet and inches, the standard method for U.S. construction documents. Metric users have changed the Precision value and kept the Decimal unit system.
Along with the unit style, you should adjust the size of the dimension text. The Text tab of the New Dimension Style dialog box lets you set a variety of text options, including text location relative to the dimension line, style, and height.
Follow these steps to set the height of your dimension text:
Click the Text tab to display the text options (Figure 12.7).
Highlight the contents of the Text Height input box.
Type ⅛
Unlike with the text you created in Chapter 10, you specify the text height by its final plot size. You then specify an overall dimension scale factor that affects the sizing of all dimensioning settings, such as text and arrows.
If you want to use a specific text style for your dimensions, select a text style in the Text Style drop-down list in the Text tab. If the style you select happens to have a height specification greater than 0, that height will override any text height settings you enter in the Text tab.
AutoCAD's default setting for the placement of dimension text puts the text in line with the dimension line, as shown in the example at the top of Figure 12.2 earlier in this chapter. However, you want the new My Architectural style to put the text above the dimension line, as is done in the center of Figure 12.2. To do that, you'll use the Text Placement and Text Alignment options in the Text tab of the New Dimension Style dialog box:
In the Text Alignment group in the lower-right corner of the dialog box, click the Aligned With Dimension Line radio button.
In the Text Placement group, open the Vertical drop-down list, and select Above. The appearance of the sample image changes to show how your new settings will look.
Again in the Text Placement group, change the Offset From Dim Line value to 1/16. This setting controls the size of the gap between the dimension line and the dimension text.
Each time you change a setting, the graphic gives you immediate feedback about how your changes will affect your dimension style.
Next, you'll specify a different type of arrow for your new dimension style. For linear dimensions in architectural drawings, a diagonal line, or tick mark, is typically used instead of an arrow.
In addition, you want to set the scale for the graphical components of the dimension, such as the arrows and text. Recall from Chapter 10 that text must be scaled up in size in order to appear at the proper size in the final output of the drawing. Dimensions too must be scaled so they look correct when the drawing is plotted. The arrows are controlled by settings in the Symbols And Arrows tab, and the overall scale of the dimension style is set in the Fit tab.
Here are the steps for specifying the arrow type and scale:
Click the Symbols And Arrows tab to display the options for controlling the arrow style and dimension line extensions (Figure 12.8).
In the Arrowheads group, open the First drop-down list and choose Architectural Tick. The graphic next to the arrowhead name shows you what the arrowhead looks like.
In the Arrowheads group, change the Arrow Size setting to ⅛. Metric users should enter .3.
Next, you need to set the behavior of the dimension line and extension lines:
Click the Lines tab to display the options for controlling the dimension and extension lines (Figure 12.9).
In the Dimension Lines group, highlight the value in the Extend Beyond Ticks input box, and enter 1/16. (Metric users should enter 0.15.) This causes the dimension lines to extend past the tick arrows. This is a standard graphic practice used for dimensioning linear dimensions in architectural plans.
In the Extension Lines group, change the Extend Beyond Dim Lines setting to 1/8. Metric users should change this to 0.3. This setting determines the distance the extension line extends past the dimension line.
Again in the Extension Lines group, change the Offset From Origin setting to 1/8. Metric users should change this to 0.3. This sets the distance from the point being dimensioned to the beginning of the dimension extension line.
Click the Fit tab of the New Dimension Style dialog box to display the options for overall dimension scale and miscellaneous settings (Figure 12.10).
Turn on the Annotative option in the Scale For Dimension Features group. You may recall from Chapter 10 that the Annotative option allows AutoCAD to scale an object automatically to the drawing's annotation scale.
Click OK to close the New Dimension Style dialog box. The Dimension Style Manager dialog box opens again.
You can use the Alternate Units tab of the New Dimension Style dialog box to set up AutoCAD to display a second dimension in centimeters or millimeters. Likewise, if you're a metric user, you can set up a second dimension to display feet and inches. The following exercise shows you how to set up alternate dimensions. You don't have to do this exercise now; it's here for your information. If you like, come back later and try it to see how it affects your dimensions. You can pick up the tutorial in the next section, "Setting the Current Dimension Style."
If you decide later that you don't want the alternate units to be displayed, you can turn them off by returning to the New Dimension Style dialog box and removing the checkmark from the Display Alternate Units check box.
Here are the steps for setting up alternate dimensions:
In the Dimension Style Manager, select a style and then click Modify. Or, if you want to create a new style, click New.
In the New Dimension Style dialog box, click the Alternate Units tab (Figure 12.11).
Click the Display Alternate Units check box. The options in the tab become available for your input.
Select the appropriate option from the Unit Format drop-down list. U.S. users should select Decimal to show metric alternate units. Metric users should select Architectural.
Select an appropriate precision value from the Precision drop-down list.
Enter a scale factor for your alternate dimension in the Multiplier For Alt Units input box. For U.S. users, the default value is 25.4. This value converts feet-and-inch dimensions to millimeters. In our metric examples, you've been using centimeters, so change this setting to 2.54. Metric users should enter 0.3937 to convert centimeters to feet and inches.
In the Placement group, select where you want the alternate dimension to appear in relation to the main dimension.
Click OK to close the New Dimension Style dialog box. The Dimension Style Manager dialog box opens again.
Before you can begin to use your new dimension style, you must make it the current default:
Click My Architectural in the Styles list box in the Dimension Style Manager dialog box.
Click the Set Current button at the far right in the dialog box.
Click Close to exit the Dimension Style Manager dialog box.
You can also select a dimension style from the drop-down list on the Annotate tab's Dimensions panel. You're now ready to use your new dimension style.
In the next set of exercises, you'll use the My Architectural style you just created. To switch to another style, open the Dimension Style Manager dialog box again, select the style you want from the Styles list, and click Set Current, as you did in the previous exercise.
To modify an existing dimension style, open the Dimension Style Manager dialog box, highlight the style you want to edit, and then click Modify to open the Modify Dimension Style dialog box (this is virtually identical to the New Dimension Style dialog box you've been working with). You can then make changes to the different components of the selected dimension style. When you've finished making changes and closed both dialog boxes, all the dimensions associated with the edited style update automatically in your drawing. For example, if you're not using the Annotative Scale feature, and you decide you need to change the dimension scale of a style, you can open the Modify Dimension Style dialog box and change the Scale value in the Scale for dimension features group of the Fit tab.
So far, you've been introduced you to the various settings that let you determine the appearance of a dimension style. I didn't discuss every option; to learn more about the other dimension style options, consult Appendix D. There you'll find descriptions of all the items in the New Dimension Style and Modify Dimension Style dialog boxes, plus reference material covering the system variables associated with each option.
If your application is strictly architectural, you may want to make these same dimension-style changes to the Acad.dwt template file or create a set of template files specifically for architectural drawings of different scales.
The most common type of dimension you'll be using is the linear dimension. The linear dimension is an orthogonal dimension measuring the width and length of an object. AutoCAD provides three dimensioning tools for this purpose: Linear (Dimlinear), Continue (Dimcont), and Baseline (Dimbase). These options are readily accessible from the Annotate tab's Dimensions panel.
In the following set of exercises, you'll see figures displaying dimensions in both Imperial and metric units. I've included both measurements so that both Imperial and metric users can more easily follow the tutorial. But in your own drawing, you'll see only one dimension value displayed above the dimension line.
Before you apply any dimension, you should study the Annotate tab's Dimensions panel (Figure 12.12). This panel contains nearly all the tools necessary to draw and edit your dimensions.
Many of the dimensioning tools discussed in this chapter can be found in the Home tab's Annotation panel. However, since the focus of this chapter is on dimensioning, unless otherwise noted, use the panels on the Annotate tab.
Let's start by looking at the basic dimensioning tool, Linear. The Linear button (the Dimlinear command) on the Annotate tab's Dimensions panel accommodates both the horizontal and vertical dimensions.
In this exercise, you'll add a vertical dimension to the right side of the Unit plan:
Before you start to dimension your drawing, you need to set the scale of your drawing. Select ¼″=1′-0″ from the Annotation Scale drop-down list. Metric users should select 1:50.
The
Specify first extension line origin or <select object>:prompt asks you for the first point of the distance to be dimensioned. An extension line connects the object being dimensioned to the dimension line. Use the Endpoint Osnap override, and pick the upper-right corner of the entry, as shown in Figure 12.13.At the
Specify second extension line origin:prompt, pick the lower-right corner of the living room, as shown in Figure 12.13.At the next prompt,
Specify dimension line location or [Mtext/Text/Angle/Horizontal/Vertical/Rotated]:, the dimension line indicates the direction of the dimension and contains the arrows or tick marks. Move your cursor from left to right to display a temporary dimension. This enables you to select a dimension-line location visually.Enter @4′<0
You'll often want to enter a group of dimensions strung together in a line. For example, you may want to continue dimensioning the balcony and align the continued dimension with the dimension you just entered.
To do this, use the Continue option found in the Dimensions panel's Continue/Baseline flyout:
At the
Specify a second extension line origin or [Undo/Select] <Select>:prompt, pick the upper-right corner of the balcony. (See the top image in Figure 12.14.)Pick the right end of the rail on the balcony. See the bottom image in Figure 12.13 for the results.
Press
If you select the wrong location for a continued dimension, you can click the Undo tool or press U
The Continue option adds a dimension from where you left off. The last-drawn extension line is used as the first extension line for the continued dimension. AutoCAD keeps adding dimensions as you continue to pick points, until you press
You probably noticed that the 5″ dimension is placed away from the dimension line with a leader line pointing to it. This is the result of the 5″ dimension's text not having enough space to fit between the dimension extension lines. You'll learn about dimension style settings that can remedy this problem. For now, let's continue adding dimensions to the plan.
Another way to dimension objects is to have several dimensions originate from the same extension line. To accommodate this, AutoCAD provides the Baseline option on the Dimensions control panel and the Dimension drop-down menu.
To see how this works, you'll start another dimension—this time a horizontal one—across the top of the plan:
At the
Specify first extension line origin or <select object>:prompt, use the Endpoint osnap to pick the upper-left corner of the bathroom, as shown in Figure 12.15.At the
Specify second extension line origin:prompt, pick the upper-right corner of the bathroom, as shown in Figure 12.15.At the
Specify dimension line location or [Mtext/Text/Angle/ Horizontal/Vertical/Rotated]:prompt, pick a point above the Unit plan, like the 7′-6″ dimension in Figure 12.15. If you need to, pan your view downward to fit the dimension in.You're set to draw another dimension continuing from the first extension line of the dimension you just drew. Click the Baseline tool on the Continue/Baseline flyout of the Dimensions panel. Or, type Dba
At the
Specify a second extension line origin or [Undo/Select] <Select>:prompt, click the upper-right corner of the entry, as shown in Figure 12.16.Press
Pan your view down so it looks similar to Figure 12.16.
In this example, you see that the Baseline option is similar to the Continue option except that the Baseline option enables you to use the first extension line of the previous dimension as the base for a second dimension. The distance between the two horizontal dimension lines is controlled by the Baseline Spacing setting in the Lines tab of the New Dimension Style and Modify Dimension Style dialog boxes.
As you work toward a deadline, you may find that you, or someone else, cut a few corners when adding dimensions and a set of parallel dimension lines isn't accurately placed.
You can quickly adjust the spacing between dimension lines using the Adjust Space tool in the Dimensions panel:
At the
Select base dimension:prompt, click the dimension closest to the feature being dimensioned.At the
Select dimensions to space:prompt, click the next dimension.Continue to select the other parallel dimensions. When you're finished with your selections, press
You see the prompt
Select dimensions to space: Enter value or [Auto] >Auto<:
Enter a value for the distance between the dimension lines. This value should be in full-scale distances. You can also press
As you add more dimensions to your drawings, you'll find that AutoCAD occasionally places the dimension text or line in an inappropriate location or that you may need to modify the dimension text. In the following sections, you'll take an in-depth look at how you can modify dimensions to suit those special circumstances that always crop up.
So far in this chapter, you've been accepting the default dimension text. You can append information to the default dimension value or change it entirely if you need to. At the point when you see the temporary dimension dragging with your cursor, enter T
Let's see how this works by changing an existing dimension's text in your drawing:
Type ED
Click the last horizontal dimension you added to the drawing at the top of the screen. The Text Editor tab appears in the Ribbon (Figure 12.17).
Press the End key to place the cursor at the end of the
14′-0″text, and then type to face of stud.Click Close Text Editor in the Close panel of the Text Editor tab, and then press
Because you don't need the new appended text for the tutorial, click the Undo button in the Quick Access toolbar to remove the appended text.
If you need to restore the original dimension text for a dimension whose value has been completely replaced, you can use the steps shown in the previous exercise. However, in step 3, replace the text with the <> bracket symbols.
You can also have AutoCAD automatically add a dimension suffix or prefix to all dimensions instead of just a chosen few by using the Suffix or Prefix option in the Primary Units tab of the New Dimension Style or Modify Dimension Style dialog box. See Appendix D for more on this feature.
AutoCAD provides the associative dimensioning capability to update dimension text automatically when a drawing is edited. Objects called definition points determine how edited dimensions are updated.
The definition points are located at the same points you pick when you determine the dimension location. For example, the definition points for linear dimensions are the extension line origins. The definition points for a circle diameter are the points used to pick the circle and the opposite side of the circle. The definition points for a radius are the points used to pick the circle plus the center of the circle.
Definition points are point objects. They're difficult to see because they're usually covered by the feature they define. You can, however, see them indirectly by using grips. The definition points of a dimension are the same as the dimension's grip points. You can see them by clicking a dimension. Try the following:
Make sure the Grips feature is turned on. (See Chapter 2 to refresh your memory on the Grips feature.)
Click the longest of the three vertical dimensions you drew in the earlier exercise. You'll see the grips of the dimension, as shown in Figure 12.18.
Making Changes to Multiple Dimensions
You can use the Dimension Edit tool to edit existing dimensions quickly. This tool gives you the ability to edit more than one dimension's text at one time. One common use for the Dimension Edit tool is to change a string of dimensions to read Equal instead of showing the actual dimensioned distance. The following example shows an alternative to using the Properties palette for appending text to a dimension:
Type Ded
At the prompt
Enter type of dimension editing [Home/New/Rotate/Oblique]<Home>:
type N
Use the arrow keys to move the cursor behind or in front of the 0, and then enter the text you want to append to the dimension. You can remove the 0 and replace the dimension with your text as an alternative.
Click Close Text Editor in the Close panel of the Text Editor tab.
At the
Select objects:prompt, pick the dimensions you want to edit. TheSelect objects:prompt remains, enabling you to select several dimensions.Press
The Dimension Edit tool is useful in editing dimension text, but you can also use this tool to make graphical changes to the text. Here is a list of the other Dimension Edit tool options:
- Home
Moves the dimension text to its standard default position and angle.
- Rotate
Rotates the dimension text to a new angle.
- Oblique
Skews the dimension extension lines to a new angle. (See the section "Skewing Dimension Lines" later in this chapter.)
The definition points, whose location you can see through their grips, are located on their own unique layer called Defpoints. Definition points are displayed regardless of whether the Defpoints layer is on or off.
To give you an idea of how these definition points work, try the following exercises that show you how to manipulate the definition points directly.
In this exercise, you'll use coordinates to move a dimension line:
With the grips visible, click the grip near the dimension text.
Move the cursor around. When you move the cursor vertically, the text moves along the dimension line. When you move the cursor horizontally, the dimension line and text move together, keeping their parallel orientation to the dimensioned floor plan. Here the entire dimension line, including the text, moves. In a later exercise, you'll see how you can move the dimension text independently of the dimension line.
Enter @9′<0
In step 3 of the previous exercise, you saw that you can specify an exact distance for the dimension line's new location by entering a relative polar coordinate. Cartesian coordinates work just as well. You can even use object snaps to relocate dimension lines.
Next, try moving the dimension line back by using the Perpendicular osnap:
Click the grip at the bottom of the dimension line you just edited.
Shift+click the right mouse button and choose Perpendicular from the Osnap shortcut menu.
Place the cursor on the vertical dimension line that dimensions the balcony and click it.
Click All from the Zoom flyout on the View tab's Navigate panel, and then click Save from the Quick Access toolbar to save this file in its current state.
The selected dimension line moves to align with the other vertical dimension, back to its original location.
In some cases, you have to change an individual dimension's style settings in order to edit it. For example, if you try to move the text of a typical linear dimension, you may find that the text and dimension lines are inseparable. You need to make a change to the dimension style setting that controls how AutoCAD locates dimension text in relation to the dimension line. The following section describes how you can change the style settings of individual dimensions to facilitate changes in the dimension.
You've seen how dimension text is attached to the dimension line so that when the text is moved, the dimension line follows. You may encounter situations in which you want to move the text independently of the dimension line. The following steps show how you can separate dimension text from its dimension line. These steps also show how you can change a single dimension's style settings:
Click the dimension you want to edit to expose its grips.
Right-click and choose Properties from the shortcut menu to open the Properties palette.
Scroll down the list of properties until you see the Fit category. If you don't see a list of options under Fit, click the downward-pointing arrow to the right to display a new set of options.
Scroll farther down the list until you see the Text Movement option to the right of the Text Movement listing, and then click this option.
Click the arrow that appears next to the Keep Dim Line With Text listing to open the drop-down list, then select the Move Text, Add Leader option (Figure 12.20).
Close the Properties palette.
In the Properties palette, the Move Text, Add Leader option in the Text Movement option of the Fit category lets you move the dimension text independently of the dimension line. It also draws a leader from the dimension line to the text. Another option, Move Text, No Leader, does the same thing but doesn't include a leader. You can also set these options for a dimension style by using the Text Placement options in the Fit tab of the New Dimension Style or Modify Dimension Style dialog box.
As you can see from these steps, the Properties palette gives you access to many of the settings you saw for setting up dimension styles. The main difference here is that the Properties palette affects only the dimensions you've selected.
In a previous exercise, you changed the format setting of a single dimension after it was placed. These settings can be made a standard part of your Architectural dimension style by using the Modify button in the Dimension Style Manager dialog box.
If you have multiple dimension styles and you want to change an existing dimension to the current dimension style, use the Update tool. Choose Update on the Dimensions panel or type -Dimstyle
Rotating and Positioning Dimension Text
Once in a while, dimension text works better if it's kept in a horizontal orientation, even if the dimension itself isn't horizontal. To rotate dimension text, click the Text Angle tool from the Annotate tab's expanded Dimensions panel, select the dimension text, and then enter an angle or select two points to indicate an angle graphically. You can also enter 0
If you need to move the dimension text to the left, center, or right of the dimension line, you can use the Left Justify, Center Justify, or Right Justify tool in the Annotate tab's expanded Dimensions panel.
It's helpful to be able to edit a dimension directly by using its grips. But the key feature of AutoCAD's dimensions is their ability to adjust themselves automatically to changes in the drawing.
To see how this works, try moving the living room closer to the bathroom wall. You can move a group of lines and vertices by using the Stretch command and the Crossing option:
At the Select objects to stretch by crossing-window or crossing-polygon... Select objects: C Specify first corner:
Pick a crossing window, as illustrated in Figure 12.21, and then press
At the
Specify base point or Displacement <Displacement>:prompt, pick any point on the screen.At the
Specify second point or <use first point as displacement>:prompt, enter @2′<90After viewing the result of using the Stretch tool, click the Undo tool in the Quick Access toolbar or type U
You can also use the Mirror, Rotate, and Stretch commands with dimensions. The polar arrays also work, and you can use Extend and Trim with linear dimensions.
When you're editing dimensioned objects, be sure to select the dimension associated with the object being edited. As you select objects, using the crossing window (C) or crossing polygon (CP) selection option helps you include the dimensions. For more on these selection options, see Chapter 2.
Modifying the Dimension Style Settings by Using Override
In the section "Moving Fixed Dimension Text," you used the Properties palette to facilitate the moving of the dimension text. You can also choose the Override tool in the Annotate tab's expanded Dimensions panel (Dimoverride command) to accomplish the same thing. The Override option enables you to change an individual dimension's style settings. Here's an example that shows how you can use the Override option in place of the Properties palette in the exercise of "Moving Fixed Dimension Text":
Press the Esc key twice to make sure you aren't in the middle of a command. Then choose Override from the Annotate tab's expanded Dimensions panel.
At the following prompt, type Dimfit
Enter dimension variable name to override or [Clear overrides]:
At the
Enter new value for dimension variable <3>:prompt, enter 4The
Enter dimension variable name to override:prompt appears again, enabling you to enter another dimension variable. PressAt the
Select objects:prompt, select the dimension you want to change. You can select a group of dimensions if you want to change several dimensions at once. Press
As you can see from this example, the Dimoverride command requires that you know exactly which dimension variable to edit in order to make the desired modification. In this case, setting the Dimfit variable to 4 lets you move the dimension text independently of the dimension line. If you find the Dimoverride command useful, consult Appendix D to determine which system variable corresponds to the Dimension Style dialog box settings.
You've seen how dimensions and the objects they're associated with can move together so that the dimension remains connected to the object. When you're in the process of editing a drawing, dimensions may lose their association with objects, so you may need to re-create an association between a dimension and an object. The following steps show you how this is done:
At the following prompt, select the dimension that you want to reassociate with an object, and then press
Select dimensions to reassociate Select Objects:
At the
Specify first extension line origin or [Select object] <next>:prompt, an X appears at one of the dimension's definition points.
Use the Endpoint osnap, and click the end of the object you want to have connected to the definition point indicated in step 3.
An X appears at the dimension's other definition point. Use the Endpoint osnap again, and click the other endpoint of the object you want associated with the dimension. You now have the dimension associated with the endpoints of the object.
In step 3, you see an X at the location of a dimension definition point. If the definition point is already associated with an object, the X appears with a box around it. The box is a reminder that the definition point is already associated with an object and that you'll be changing its association. In this situation, you can press
Also in step 3, you have the option to select an object. This option enables you to associate the dimension with an entire object instead of with just one endpoint. If you type S
AutoCAD provides a method for creating a string of dimensions by using a single operation. The Qdim command lets you select a set of objects instead of having to select points. The following exercise demonstrates how the Qdim command works:
If you haven't done so already, zoom out so you have an overall view of the
Unitfloor plan.
At the
Select geometry to dimension:prompt, place a selection window around the entire left-side wall of the unit.Press
Specify dimension line position, or [Continuous/Staggered/Baseline/Ordinate/Radius/Diameter/ datumPoint/Edit/seTtings] >Continuous<:
Click a point to the left of the wall to place the dimension. A string of dimensions appears, displaying all the dimensions for the wall (Figure 12.23).
When you've finished reviewing the results of this exercise, exit the file without saving it.
The prompt in step 4 indicates several types of dimensions you can choose from. For example, if you want the dimensions to originate from a single baseline, you can enter B
The Qdim command can be a time-saver when you want to dimension a wall quickly. It may not work in all situations, but if the object you're dimensioning is fairly simple, it can be all you need.
In this exercise, you used a simple window to select the wall. For more complex shapes, try using a crossing polygon selection window. See Chapter 2 for more on crossing polygons.
You may eventually encounter a drawing that contains alternate dimensions, as shown in some of the figures earlier in this chapter. You can remove those alternate dimensions by turning off the alternate dimension features. Here's how it's done:
The dimensions that use the style you just edited change to remove the alternate dimensions. You can also perform the reverse operation and add alternate dimensions to an existing set of dimensions. Follow the steps shown here, but instead of removing the checkmark in step 4, add the checkmark, and make the appropriate setting changes to the rest of the Alternate Units tab.
So far, you've been reading about how to work with linear dimensions. You can also dimension non-orthogonal objects, such as circles, arcs, triangles, and trapezoids. In the following sections, you'll practice dimensioning a non-orthogonal object.
For the following exercises, you'll use a drawing of a hexagonal-shaped window. Open the 12a-wind.dwg file from the sample files; metric users should open the 12a-wind-metric.dwg file. You can use this file to follow along.
Now you'll dimension the window. The unusual shape of the window prevents you from using the horizontal or vertical dimensions you've used already. However, choosing Aligned from the Dimension flyout in the Dimensions panel enables you to dimension at an angle:
At the
Specify first extension line origin or <select object>:prompt, pressAt the
Select 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 a circle for this type of dimension.At the
Specify dimension line location or [Mtext/Text/Angle]:prompt, pick a point near coordinate 2′-10″,2′-2″ (90,60 for metric users). The dimension appears in the drawing as shown in Figure 12.24.
Just as with linear dimensions, you can enter T
Next, you'll dimension a face of the hexagon. Instead of its actual length, however, you'll dimension a distance at a specified angle—the distance from the center of the face:
Click the Linear tool from the Dimension flyout on the Dimensions panel or type Dli
At the
Specify first extension line origin or <select object>:prompt, pressAt the
Select object to dimension:prompt, pick the lower-right face of the hexagon near coordinate 2′-6″,1′-4″ (77,33 for metric users).At the
Specify dimension line location or [Mtext/Text/Angle/Horizontal/Vertical/Rotated]:prompt, type RAt the
Specify angle of dimension line <0>:prompt, enter 30At the
Specify dimension line location or [Mtext/Text/Angle/Horizontal/Vertical/Rotated]:prompt, pick a point near coordinate 24′-11″,0′-8″ (88,12 for metric users). Your drawing will look like Figure 12.25.
The Dimrotate command accomplishes the same thing with a slight change in the sequence of steps.
To dimension circular objects, you use another set of options from the Dimension menu:
At the
Select arc, circle, line, or <specify vertex>:prompt, pick the upper-left face of the hexagon near coordinate 1′-3″,1′-10″ (44,57 for metric users).At the
Select second line:prompt, pick the top face at coordinate 1′-9″,2′-2″ (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 corner of the hexagon, the dimension changes, as shown in the top images of Figure 12.26.Pick a point near coordinate 1′-9″,1′-11″ (49,50 for metric users). The dimension is fixed in the drawing. (See the bottom image of Figure 12.25.)
If you need to make subtle adjustments to the dimension line or text location, you can do so using grips after you place the angular dimension.
Now try the Diameter option, which shows the diameter of a circle:
At the
Select arc or circle:prompt, pick the circle.At the
Specify dimension line location or [Mtext/Text/Angle]:prompt, you see the diameter dimension drag along the circle as you move the cursor. If you move the cursor outside the circle, the dimension line and text also move outside the circle. (See the top image in Figure 12.27.)
If the dimension text can't fit in the circle, AutoCAD gives you the option to place the dimension text outside the circle as you drag the temporary dimension to a horizontal position.
Place the cursor inside the circle so the dimension arrow points in a horizontal direction, as shown in the bottom image of Figure 12.27.
With the text centered, click the mouse.
Figure 12.28 shows a radius dimension on the outside of the circle, but you can place it inside in a manner similar to how you place the diameter dimension. The Center Mark tool on the expanded Dimensions panel places a cross mark in the center of the selected arc or circle.
If you need to dimension an arc or a circle whose center isn't in the drawing area, you can use the jogged dimension. Here are the steps:
At the
Select arc or circle:prompt, select the object you want to dimension.At the
Specify center location override:prompt, select a point that indicates the general direction to the center of the arc or circle. A dimension line appears and follows the movement of your cursor.Position the dimension line where you want it, and then click.
Position the dimension line jog where you want it, and then click. The jogged dimension is placed in the drawing (Figure 12.29).
Arc lengths can also be given a dimension using the Arc Length tool. Choose the Arc Length tool from the Dimension flyout on the Dimensions panel, or enter Dar
At times, you may need to force the extension lines to take on an angle other than 90° to the dimension line. This is a common requirement of isometric drawings, in which most lines are at 30° or 60° angles instead of 90°. To facilitate non-orthogonal dimensions like these, AutoCAD offers the Oblique option:
At the
Select objects:prompt, pick the aligned dimension in the upper-right portion of the drawing, and pressAt the
Enter obliquing angle (Press ENTER for none):prompt, enter 60 for 60°. The dimension will skew so that the extension lines are at 60° (Figure 12.30).Save the drawing, and exit AutoCAD.
One type of dimension is something like a text-dimension hybrid. The AutoCAD Multileader tool lets you add a text note combined with an arrow that points to an object in your drawing. Multileaders are easy to use and offer the same text-formatting tools as the Mtext tool. Try the following exercise to get familiar with multileaders:
At the
Specify leader arrowhead location or [leader Landing first/Content first/Options] <Options>:prompt, pick a point near the top-left edge of the hexagon at coordinate 1′-4″,2′-0″ (45,59 for metric users).At the
Specify leader landing location:prompt, enter @6<110Enter Window Frame for the note, and then click Close Text Editor in the Text Editor tab's Close panel. Your note appears with the leader arrow similar to the one in Figure 12.32.
The text in the note is in the current text style unless you specify another style in the Text tab of the New Dimension Style Or Modify Dimension Style dialog box. (See the section "The Text Tab" in Appendix D for more information.)
The Multileader tool offers a lot of options that aren't obvious when you're using it. In step 2 of the previous example, after choosing Multileader, you can press
Enter an option [Leader type/leader lAnding/Content type/Maxpoints/First angle/Second angle/eXit options] >eXit options<:
Table 12.1 gives you a rundown of these options and their functions.
Table 12.1. The Multileader Options
Besides using the options shown in Table 12.1, you can create multileader styles to control the appearance of multileaders. Multileader styles are similar in concept to text and dimension styles. They allow you to set up the appearance of the leader under a name that you can call up anytime. For example, you may want to have one type of leader that uses a block instead of text for the note and another leader that uses a dot in place of an arrow. Alternatively, you may want to set up a style that uses curved lines instead of straight ones for the leader line. You can create a multileader style for each of these types of leader features and then switch between the leader styles, depending on the requirements of your leader note.
When you click Modify or New, the Modify Multileader Style dialog box opens (see Figure 12.34).
Table 12.2 describes the options in each of the tabs of the Modify Multileader Style dialog box. Some of these options are the same as those for the Multileader command.
Table 12.2. The Modify Multileader Style Dialog Box Options
Function | |
|---|---|
General | Lets you set the leader line to straight or curved. You can also set the color, lineweight, and linetype for the leader line. |
Arrowhead | Controls the arrowheads. |
Leader Break | Controls the size of the gap in a leader line when the Leaderbreak command is applied. Leaderbreak places a break on a leader line where two leader lines cross. |
Constraints | Determines the number of line segments in the leader line. You can also apply angle constraints to the leader-line segments. |
Landing Settings | Controls the leader-line landing segment. This is the last line segment that points to the note. |
Scale | Lets you control the scale of the leader components. You can either apply a fixed scale or use the Annotative option to have the drawing annotation scale apply to the leader. |
Multileader Type | Lets you select the type of object that will be used for the leader note. The options are Mtext, Block, and None. |
Text Options | Gives you control over the way the leader note appears. You can control color, text style, size, justification, and orientation. |
Leader Connection | Determines the position between the leader line and the note. |
Once you've set up a multileader style, you can set it up as the default style by selecting it from the Multileader Style drop-down list on the Annotate tab's Leaders panel.
The selected style will be applied to any new multileader you add to your drawing. You can also change the style of an existing multileader. To do this, click the multileader to select it, and then select the multileader style you want from the Leaders panel drop-down list.
If you need to make changes to the note portion of a multileader, you can do so by double-clicking the note. This brings up the Text Editor tab in the Ribbon, allowing you to make changes as in a word processor.
At other times, you may want to change the leader line, arrows, or other graphic features of the multileader. For example, you may want to have all the notes aligned vertically for a neater appearance. As another option, you may want to add more leader arrows so the note points to several objects in the drawing instead of just one as another option.
The Leaders panel offers several tools that let you make these types of changes to your leader notes (see Figure 12.31). The Add Leader and Remove Leader tools let you add or remove leaders from a multileader. The Add Leader tool is a handy tool if you want a single note to point to several objects. The Align tool lets you align the note portion of several multileaders. Finally, the Collect tool lets you collect several multileaders that use blocks for notes into a single note.
In a crowded drawing, your multileader arrow may have to cross over a dimension line. In many drafting conventions, when a leader line crosses over a dimension line, the dimension line must be shown with a gap.
You can apply a gap to a dimension line using the Dimbreak tool. Here's how it works:
At the
Select dimension to add/remove break or [Multiple]:prompt, select a dimension line, or enter MWhen you're finished with your selection, press
At the
Select object to break dimension or [Auto/Restore/Manual] <Auto>:prompt, press
If you prefer to indicate a break manually, enter M
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 12.35 shows a typical application of ordinate dimensions. In the lower-left corner, note the two dimensions whose leaders are jogged. Also note the origin location in the upper-right corner.
To use AutoCAD's Ordinate command, perform the following steps:
At the
Specify new origin point <0,0,0>:prompt, click the exact location of the origin of your part.
At the
Specify feature location:prompt, click the item you want to dimension. The direction of the leader determines whether the dimension will be of the Xdatum or the Ydatum.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'll get a chance to work with the UCS feature in Chapter 22.
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 Text Editor tab in the Ribbon, enabling you to append or replace the ordinate dimension text. The Text option lets you enter replacement text directly through the Command window.
If you turn off Ortho mode, the dimension leader is drawn with a jog to maintain the orthogonal (look back at Figure 12.35).
In mechanical drafting, tolerances are a key part of a drawing's notation. They specify the allowable variation in size and shape that a mechanical part can have. To help facilitate tolerance notation, AutoCAD provides the Tolerance command, which offers common ISO tolerance symbols together with a quick way to build a standard feature-control symbol. Feature-control symbols are industry-standard symbols used to specify tolerances. If you're a mechanical engineer or drafter, AutoCAD's tolerance notation options will be a valuable tool. However, a full discussion of tolerances requires a basic understanding of mechanical design and drafting and is beyond the scope of this book.
This is where you enter tolerance and datum values for the feature-control symbol. You can enter two tolerance values and three datum values. In addition, you can stack values in a two-tiered fashion.
Click a box in the Sym group to open the Symbol dialog box.
The top image in Figure 12.37 shows what each symbol in the Symbol dialog box represents. The bottom image shows a sample drawing with a feature symbol used on a cylindrical object. The symbols in the sample drawing show that the upper cylinder needs to be concentric within 0.0003″ of the lower cylinder.
In the Geometric Tolerance dialog box, you can click a box in any of the Datum groups or a box in the right side of the Tolerance groups to open the Material Condition dialog box. This dialog box contains standard symbols relating to the maximum and minimum material conditions of a feature on the part being dimensioned.
Another type of dimension related to tolerances is the inspection dimension. This is a type of dimension notation that indicates how often the tolerances of a dimension should be checked.
To add an inspection dimension, first add a regular linear dimension as described in the early part of this chapter. Next, follow these steps:
The dimension appears with the additional changes from the dialog box (Figure 12.39).
- Understand the components of a dimension
Before you start to dimension with AutoCAD, it helps to become familiar with the different parts of a dimension. This will help you set up your dimensions to fit the style of dimensions that you need.
- Master It
Name a few of the dimension components.
- Create a dimension style
As you become more familiar with technical drawing and drafting, you'll learn that there are standard formats for drawing dimensions. Arrows, text size, and even the way dimension lines are drawn are all subject to a standard format. Fortunately, AutoCAD offers dimension styles that let you set up your dimension format once and then call up that format whenever you need it.
- Master It
What is the name of the dialog box that lets you manage dimension styles, and how do you open it?
- Draw linear dimensions
The most common dimension that you'll use is the linear dimension. Knowing how to place a linear dimension is a big first step in learning how to dimension in AutoCAD.
- Master It
Name the three locations you're asked for when placing a linear dimension.
- Edit dimensions
Dimensions often change in the course of a project, so you should know how to make changes to dimension text or other parts of a dimension.
- Master It
How do you start the command to edit dimension text?
- Dimension non-orthogonal objects
Not everything you dimension will use linear dimensions. AutoCAD offers a set of dimension tools for dimensioning objects that aren't made up of straight lines.
- Master It
Name some of the types of objects for which a linear dimension isn't appropriate.
- Add a note with a leader arrow
In addition to dimensions, you'll probably add lots of notes with arrows pointing to features in a design. AutoCAD offers the multileader for this purpose.
- Master It
What two types of objects does the multileader combine?
- Apply ordinate dimensions
When accuracy counts, ordinate dimensions are often used because they measure distances that are similar to coordinates from a single feature.
- Master It
What AutoCAD feature do you use for ordinate dimensions that isn't strictly associated with dimensions?
- Add tolerance notation
Mechanical drafting often requires the use of special notation to describe tolerances. AutoCAD offers some predefined symbols that address the need to include tolerance notation in a drawing.
- Master It
How do you open the Geometric Tolerance dialog box?