by Paul Richard and Jim Fitzgerald

Chapter 13 – Dimensioning Drawings

• Control dimension associativity

• Create different types of dimension objects

• Create Leader Notes

• Create and manage dimension styles

• Create dimensions that match industry standards

• Create and manage dimension styles

• Update dimensions

• Match the settings of an existing dimension style

The most common dimension tools are located on the Dimension flyout menu on the Annotation panel on the Home tab of the ribbon for easyaccess

NOTEDimensions can be placed in either model space or layout (paper) space in AutoCAD. The decision of where to place dimensions (model or paper space) can be a hotly debated topic in the AutoCAD world. Regardless of how dimensioning is handled, the important thing is to maintain consistency among drawings for any given project. Your company’s CAD standards should provide clear guidelines for how dimensioning should be handled and where dimensions should be placed.

NOTEDimensions can be placed in either model space or layout (paper) space in AutoCAD. The decision of where to place dimensions (model or paper space) can be a hotly debated topic in the AutoCAD world. Regardless of how dimensioning is handled, the important thing is to maintain consistency among drawings for any given project. Your company’s CAD standards should provide clear guidelines for how dimensioning should be handled and where dimensions should be placed.

There are many types of dimension objects available in AutoCAD.

• REASSOCIATE

• Defpoints

NOTEThe Defpoints layer is unique in that it doesn’t plot, regardless of its Plot/Noplot layer setting. Also, once created, the Defpoints layer sometimes cannot be deleted with either the PURGE command or the Delete Layer button in the LAYER

NOTEThe Defpoints layer is unique in that it doesn’t plot, regardless of its Plot/Noplot layer setting. Also, once created, the Defpoints layer sometimes cannot be deleted with either the PURGE command or the Delete Layer button in the LAYER

Dimension objects are linked to the geometry and update automatically when the geometry changes.

• DIMLINEAR command

• Selecting Definition Points

Selecting an Object

NOTEWhen selecting an object, you can select only line, arc, or circle objects. Ellipses, text points, or spline curves are not allowed. When you select a polyline object, AutoCAD will dimension the line or arc segment of the polyline at the point you selected.

NOTEWhen selecting an object, you can select only line, arc, or circle objects. Ellipses, text points, or spline curves are not allowed. When you select a polyline object, AutoCAD will dimension the line or arc segment of the polyline at the point you selected.

Selecting the definition points

Linear dimensions

• Mtext and Text for overriding dimension values

• The <> Brackets

NOTEJust because you can overwrite dimension text doesn’t mean you should. When you overwrite the calculated dimension by either erasing or typing over the <> brackets, all dimension associativity is lost, so that if the drawing changes the dimension text remains the same and does not reflect the actual size of the object anymore. This situation should be avoided at all costs because eventually it will come back to haunt you.

NOTEJust because you can overwrite dimension text doesn’t mean you should. When you overwrite the calculated dimension by either erasing or typing over the <> brackets, all dimension associativity is lost, so that if the drawing changes the dimension text remains the same and does not reflect the actual size of the object anymore. This situation should be avoided at all costs because eventually it will come back to haunt you.

• Two definition points

• Line, arc or circle options

• Mtext, Text and Angle options

• The DIMRADIUS command

• The DIMRADIAL command

• The DIMJOGGED command

• The DIMDIAMETER command

Diameter Dimension

Diameter dimensions are placed with the DIMDIAMETER command. The DIMDIAMETER command behaves just like the DIMRADIUS command. The only difference is that text shown is the diameter of the arc or circle, and AutoCAD places the diameter symbol in front of the text.

• The DIMARC Command

• The Partial option

• Creating Center Marks

• It is now possible to dimension an arc beyond its endpoints. (AutoCAD automatically creates an arc extension line)

NOTE: When using the DIMCENTER command, the resulting lines are not dimension objects but simply line segments.

NOTE: When using the DIMCENTER command, the resulting lines are not dimension objects but simply line segments.

The DIMCENTER command places orthogonal line segments at the center of a circle or arc segment.

The DIMANGULAR CommandAngular dimensions are placed with the DIMANGULARcommand. When using this command, you have three options for defining angular dimension: selecting an arc or circle, selecting two intersecting lines, or picking three points to define the vertex and the two endpoints.

• Baseline Dimension

• Continued Dimension

There are actually three levels of associativity for a dimension object. The DIMASSOC system variable controls which level of dimension associativity AutoCAD uses:

• The DIMASSOC system variable can be set to a value of 0, 1, or 2.

• When DIMASSOC is set to 1, AutoCAD still creates associative dimensions, but the defpoints are not associated with any particular geometry.

• When DIMASSOC is set to 0, AutoCAD creates exploded dimensions with no associativity. No

• When set to 2 (the default setting), dimension defpoints are associated with objects in the drawing

AssociativeDimensioningCheck Box

You can toggle the DIMASSOC variable with the Associative Dimensioningcheck box in the User Preferences tab of the Options dialog box.

The Break tool allows you to break dimension or extension lines where they intersect other dimensions or objects in your drawing.

NOTEWhen you break a dimension either by selecting objects or by using the Auto option, the breaks will automatically update when the intersection point moves. If the objects are moved so that they no longer intersect, the break will disappear; if they are moved back, the break will automatically return to the original location.

NOTEWhen you break a dimension either by selecting objects or by using the Auto option, the breaks will automatically update when the intersection point moves. If the objects are moved so that they no longer intersect, the break will disappear; if they are moved back, the break will automatically return to the original location.

The Jog Line tool allows you to add a jog, or breakline, to linear dimensions to represent measurements whose values are not the same length as the dimension line.

NOTEThe linear jog size can be specified on the Symbols and Arrows tab of the DimensionStyle Manager dialog box explained later. The default is 1.5 x text height.

NOTEThe linear jog size can be specified on the Symbols and Arrows tab of the DimensionStyle Manager dialog box explained later. The default is 1.5 x text height.

The Adjust Space tool allows you to evenly space selected dimension

The QDIM Command

• Continuous• Staggered• Datum Point • Baseline• Ordinate• Radius• Diameter• Edit• Settings

Staggered quick dimensions Baseline quick dimensions

• The MLEADER Command

• Leader Settings

• Annotation, Leader Line & Arrow and Attachment.

The Add Leader tool allows you to add one or more leaders and arrowheads to an existing multileader object so that it points to multiple features. All the additional leader lines remain associated with the original leader so that if the text moves, so do the leader lines.

The Remove Leader tool allows you to remove one or more leaders from an existing multileader.

The Multileader Align tool allows you toquickly align a group of leaders along a line that you specify

The Multileader Collect tool allows you to collect and combine multiple blocks so that they are attached to one landingline

• The TOLERANCE Command

• ASME Y14.5M

• GDT.SHX font

Inspection dimensions allow you to communicate how often manufactured parts should be checked to ensure that the tolerances of a part stay within the range specified in the dimension value. This is done using an inspection label, dimension value, and inspection rate

• The DIMSTYLE command

• The Dimension Style Manager dialog box

• The New Dimension Style dialog box

• The Modify Dimension Style dialog box

• Lines Settings• Symbols and Arrows• Text• Fit• Primary Units• Alternate Units• Tolerances

The Tolerances Tab allows you to control the display and values of tolerances for both primary and alternate units.

The method setting controls:

A dimension override allows you to make changes to dimension settings without applying them to the dimension style.

NOTEA dimension override is similar to hard-coding object properties. For example, Chapter 6showed how an object can have color, linetype, lineweight, and transparency settingsthat are different from the layer setting.

NOTEA dimension override is similar to hard-coding object properties. For example, Chapter 6showed how an object can have color, linetype, lineweight, and transparency settingsthat are different from the layer setting.

• The DDEDIT Command

• The Oblique Tool

The DDEDIT command works on dimension objects as well as regular text and mtext objects. Simply select the dimension object when you are prompted to Select annotation object: AutoCAD will display the dimension text in the multiline text editor. AutoCAD’s default dimension text will appear highlighted. You can place additional text before or after the default text, or replace it altogether.

The Oblique tool allows you to adjust the angle of the extension lines for linear dimensions using the Oblique option of the DIMEDIT command. The Oblique tool is useful when extension lines conflict with other features of the drawing or you need to dimension an isometric drawing.

The Align Text tools allow you to relocate or rotate dimension text using any of the DIMTEDIT command options described in the following table.

“AutoCAD provides a means to change dimension associativity with the DIMREASSOCIATE command”

NOTE: The DIMREASSOCIATE command only works with dimension objects. If a dimension is exploded or created when the DIMASSOC system variable is set to 0, the dimension text, lines and arrows are no longer dimension objects and cannot be reassociated.

The MATCHPROP command can be used to match the dimension style properties of an existing dimension object.

The Property Settings dialog box

AutoCAD lists the current dimension style, along with any overrides, in the Command Window

NOTEThe Dimension Update tool is not technically a command. It is actually the Apply optionof the -DIMSTYLE command, which is the command window version of the DIMSTYLEcommand. When you select this tool, AutoCAD starts the -DIMSTYLE command and automatically selects the Apply option.

NOTEThe Dimension Update tool is not technically a command. It is actually the Apply optionof the -DIMSTYLE command, which is the command window version of the DIMSTYLEcommand. When you select this tool, AutoCAD starts the -DIMSTYLE command and automatically selects the Apply option.