A Trio of Dimensioning Tips
With the latest release of AutoCAD® 2016, Autodesk has introduced many new features including enhancements for dimensioning. Although dimensioning is not a new topic, there are some tools which are rarely used or overlooked despite the great features they offer. This article will introduce three dimensioning tools to you. These include the DIM command, which is the latest addition in AutoCAD’s arsenal.
DIM for AutoCAD 2016
The DIM command can perform several tasks with only one command. You can use this tool to create linear, angular, radial, baseline, and ordinate dimensions. Once you select any geometry after selecting the DIM (command equivalent of dimension tool), a corresponding output will appear at your cursor. For example, if you select a line, length will accompany the cursor and if you select a circle, diameter will accompany your cursor. Let’s explore some options available with the DIM command.
Select this tool using the big Dimension symbol from the Annotate tab, Dimensions panel or directly from the Annotation panel of the Home tab.
Once the tool is selected, bring your cursor close to a line, arc, or circle and you will notice the dimension adapts accordingly, giving you relevant output. You can create vertical and horizontal dimensions by moving your cursor in a vertical or horizontal direction after selecting a line. If the selected line is inclined to a certain angle then an inclined linear dimension will appear. You can also force this dimension to show a vertical or horizontal dimension by pressing the shift key. Press and hold the shift key and then move your cursor to restrict your dimension to a vertical or horizontal dimension—even if the line is inclined.
For creating angular dimensions, click two lines that are not parallel to each other, then click on the drawing area to place the dimension. If the lines are parallel you will see the distance between these parallel lines instead of an angle.
This command also offers the ability to create baseline and continuation dimensions. For creating baseline dimensions, create a dimension first and then select “Baseline” from the subcommand that appears on the command line, and then select the dimension you created in the previous step and click on consecutive points. Similarly, for creating continuous dimensions, make a linear dimension, then start the DIM command and select “Continue from dimension line” and click on the consecutive points.
You can also use ordinate from subcommands to create ordinate (X and Y coordinates) point dimensions. Select ordinate from the subcommands on the command line and click a point to find its ordinate. Place this dimension horizontally to find out its equivalent Y coordinate and place your cursor on a vertical line to find its equivalent X coordinate.
Using Align from the Options subcommand, you can align dimensions in the same line with respect to the selected base dimension. Start the DIM command, then select Align from Subcommand Options and click on the base dimension whose position and alignment you want to keep fixed. Then click on other dimensions you want to align to the base dimension and press Enter to exit this command.
The Distribute subcommand on the command line can be used to distribute multiple parallel dimensions with equal distance between them. This command offers you two options: equal and offset. If you select equal, then all dimensions will get equally spaced in between the most extreme dimensions. If you select offset, then dimensions will get spaced according to the distance set by the DIMDLI system variable. You can change the spacing between dimensions using the DIMDLI system variable.
Using the Layer subcommand you can decide the layer on which your dimension will be placed. You can decide layer assignments of dimension using three options.
Select the Layer subcommand from the DIM command and click on any object whose layer you want to assign to your dimension, and then make the dimension.
Select the Layer subcommand from the DIM command and type the name of the layer on the command line and press Enter. Select the object for dimensions and your dimensions will be place on that layer.
Before picking the DIM command, change the current layer to the layer on which you want to create dimensions. Then select the Layer subcommand from the DIM command and type “.” (excluding quotes) and press Enter twice. This will create your dimension on the current layer.
Making Custom Arrows for Dimension and Leader Lines
This feature is not new to AutoCAD users, but in my opinion it is often ignored. AutoCAD offers a great feature of adding your own geometrical shapes as custom arrow styles. This can be used if you have a requirement for a specially designed arrow for your new project. You can make custom arrows using AutoCAD blocks and then those arrows can be used in dimensions and leader lines. Annotative blocks can’t be used as custom arrows. These arrows also maintain their original scale in a drawing so it is advisable to choose an appropriate scale for custom arrows with respect to overall drawing scale.
For making a custom arrowhead, make a block with the required arrow shape then type DIMSTYLE on the command line and select the dimension style you want to modify and click on the Modify button. Select the Symbols and Arrows tab and then select User Arrow from the Arrow drop-down menu of the Arrowheads panel. Select Custom Arrow Block and a window will pop up with a drop-down menu containing a list of all blocks that can be used to create the arrowhead.
Select the appropriate arrow from this menu, click OK, and close all open windows. Now use the modified dimension style to create dimensions and you will see the custom arrow replacing standard arrows. A similar procedure can be used to create custom arrowheads for leader lines as well.
Adding Tolerances in AutoCAD Dimensions
Tolerance notations can be easily added to AutoCAD dimensions and can be modified like common dimensions. To add tolerances with AutoCAD dimensions, type DIMSTYLE on the command line and press Enter. Select the dimension style with which you want to associate tolerance notation and click on the Modify button, then select the Tolerance tab from the Modify Dimension Style window.
Select the method of tolerance from the Method drop-down menu of the Tolerance Format panel. The figure below shows how different formats of tolerances look.
Select your preferred method of tolerancing and then select the precision of tolerance from the Precision drop-down menu. Select the upper and lower value of tolerances from the respective option box. For the symmetrical tolerance type you will observe that one of the tolerance value is greyed, indicating that you need to define only one limit for it. Click OK once you have made all adjustments to the dimension style and close the Dimension Style Manager window.
Jaiprakash Pandey is a Mechanical Engineer, blogger, corporate trainer, and educator. He has worked in the diecast industry and many training institutions and delivered training to corporate clients in CAD software, primarily AutoCAD. Jaiprakash is currently working as senior analyst (CAD) for Ramboll, a leading engineering and design consulting group. You can reach him with comments or questions at his blog, SourceCAD.
