Here’s how to master AutoCAD’s state-of-the-art dimensioning capability.
AutoCAD is strong at annotation and detailing. It is one of its strengths. Dimensioning in AutoCAD is easy, right? Pick a couple of points, select where you want the dimension, wash, rinse and repeat.
But if it’s so easy, why does it take so long? There are so many picks to make.
You want to get it right. The dimension is essential information on a drawing. Without it, how does it get built? You want it to look professional, clean and precise and be easy to read.
So how do we get that done quickly without looking like we rushed it?
Dimensioning Efficiently
AutoCAD dimensioning is semiautomatic. You do not need to create the extension lines, dimension lines, arrowheads and other objects individually. With a couple of clicks, AutoCAD generates the dimension. The components of the dimension remain as a group so that you can make changes easily.
The base workflow is this: Start the dimensioning feature. Pick the points to dimension from. Then select where to place the dimension.
Pro tip: Never dimension without Object Snaps.
Did you know that after starting the command, you can press Enter and select an object? This grabs the endpoints of the object and you can go directly to placing the dimension.
When placing the dimensions, you can snap to the existing dimensions to help locate the new dimensions … even if the dimensions do not touch. This streamlines the process of aligning dimensions and keeps the drawing looking professional.
Many drafting standards define the distances that dimensions need to be away from the objects. Make this easier on yourself by using Object Snap Tracking and Direct Distance Entry. With this, you can locate dimensions at specific distances from the objects.
After placing the first dimension, use Baseline or Continue to build the rest in the series.
DIMCONTINUE starts from the extension of the previous (or selected) extension line. It then adds colinear (aligned)-running dimensions as you select points.
DIMBASELINE works like DIMCONTINUE but adds the dimensions all measured from the same origin. Each new dimension offsets from the last. The offset amount is set in the dimension style.
Grips
Grips are underutilized in AutoCAD. With dimensions, you can use the grips to adjust the position of the text or dimension. There is no command to start this process, so you just pick-and-go.
The grip menu supplies options for adjusting the dimension.
The text grip allows you to move the text independently from the dimension line, attach a leader and reset the text back to home (among other options).
Use the arrowhead grip to flip the arrowhead and start a new baseline or continued dimensions.
Making Changes
With Stretch, you can move a group of dimensions. Do not forget that crossing is right to left. The crossed extension lines stretch. The selected dimension objects (lines, text and arrowheads) move to the new location.
The addition of new objects can lead to unneeded dimensions. It might be surprising, but you can trim a dimension. The resultant dimension may not be associative, so you may need to associate it after the fact.
Edit the dimension text by double-clicking it. If you do not touch the highlighted value, the measurement will still be associated with it. Edit the text when you need to append text, like “TYP” or “4-PLACES”.
The expanded Dimensions panel supplies tools for changing the text alignment. You can justify the text left, center or right. The benefit is that it is faster than moving the text by hand. Plus, AutoCAD keeps the spacing consistent.
To adjust space dimensions (linear and angular), use Adjust Space (DIMSPACE). Follow this process:
- Select the base dimension; the dimension to fix and have the other dimensions move about
- Select the dimensions to space (move)
- Enter the space amount
For the space value, enter the desired offset. You can enter zero(0) when you want to align dimensions (continuous). With the Auto option, AutoCAD uses double the base dimension’s text height.
AutoCAD applies the spacing to parallel linear dimensions or angular dimensions that share a common vertex.
A Is for Awesome Dimensioning
In the options, you set the dimension behavior: nonassociative (legacy) or associative.
When a dimension is associative, it automatically updates with changes to the geometry. This is a big deal because it reduces the time needed to update drawings with changes.
There are processes that break associativity, for example, deleting an object. This is why AutoCAD supplies DIMREASSOCIATE. Use this to reassociate dimensions with objects or points in the drawing. This also works to associate dimensions that were never associated with geometry.
After selecting the dimensions, AutoCAD highlights each dimension in turn. It also marks the current association:
- An X shows no current association. Select the desired association (point or object).
- An X in a box shows there is an association. Select a new association or press Enter to accept the association and move onto the next marker.
By making something annotative in AutoCAD, it adjusts in size with changes to the scale. For annotation-related objects, you define the desired paper height. The annotation scale sets how they should display.
An object can have multiple scales applied. And you can position each scaled version independently. So what? You can have the same object appear in viewports at different scales, yet the annotation will be the same size.
Want to see more on annotation scales? Check out AutoCAD’s Hidden Gem: Annotation Scale.
DIM for the Win
DIM is an all-in-one dimensioning command that creates dimensions based on the inputs the location placed.
Hover over an object to let AutoCAD decide the best dimension type for the object or pick points to create dimensions between objects.
Use the right-click menu options to create angular, baseline and continuous dimensions. When placing a dimension on top of an existing dimension, AutoCAD prompts will ask what to do:
- Move away—configures the dimensions into a baseline grouping
- Break up—splits the existing dimension and arranges the two dimensions continuously
- Replace—removes the existing dimension and inserts the new dimension in its place
- None—does nothing and creates the new overlapping dimension
More on Dimensioning
By default, AutoCAD uses the active layer for your dimensions. It is common to place dimensions and other annotations on their own layer. Using DIMLAYER, you can set the default layer for dimensions. This way, your dimensions will be placed on the desired layer, regardless of the current layer.
To quickly dimension multiple objects, consider using Quick Dimension (QDIM). This command creates baseline or continued dimensions for selected objects. After selecting the objects, choose the style. Then pick the placement.
QDIM also works great for rearranging and changing the style of existing dimensions. Even if they were not originally created with QDIM.
Adding a space to a dimension where it crosses another object creates a dimension break. Adding this break can make it clearer and keep the dimension from looking like it is part of the drawn entities.
A long time ago, the only way to do this was to explode your dimensions and use tools like trim and break to create the gap. The dimension was no longer grouped, nor was it associative. Now we can use DIMBREAK and add the break without breaking the dimension.
The process is as follows:
- Select the dimension(s) to break. Use the Multiple option when you want to select more than one dimension.
- Select the object (including other dimensions) to break with.
Instead of selecting objects, use Auto to break the selected dimensions at all intersections. Use Manual to pick two points to set where the dimension will break.
DIMBREAK works with most dimension types. The break is associative. It updates as the broken dimension or intersecting object changes. Set the break size in the dimension style.
Dimension Styles control the appearance and behavior of your dimensions. Did you know you can create styles for specific types of dimensions?
After selecting New, as opposed to setting the name, select the type of dimension to “User for.” Here I am creating a child style just for Radius dimensions.
As I dimension, AutoCAD automatically applies the child style as I dimension radii.
It honors the parent style, meaning changes to the parent propagate to the non-overwritten settings in the child.
Want to learn more? Check out 4 Little-Known AutoCAD Dimensioning Tips by Jaiprakash Pandey.