Understanding AutoCAD Mechanical Object Snap Settings

12 Feb, 2013 By: John Hackney

IMAGINiT Tricks Tutorial: Do you ever feel like your object snaps are possessed? If you are experiencing odd behavior while using them, this tip can help.

Editor's note: This tutorial courtesy of IMAGINiT Technologies.

AutoCAD Mechanical has a truly wonderful set of commands and settings that make it a superior tool for CAD work. There are times when some of these settings can baffle the best of us, however, unless we understand the option settings in the program. In the image below, you can see I do not have object snaps turned on, and do not have any selected.

When I start the Line command, and move by objects on the screen, I see object snap markers. At this point two possible thoughts arise, "I have done something wrong in the program configuration," or "The program is malfunctioning."

AutoCAD Mechanical has two methods of assigning object snaps: System Settings and User Settings. If you are experiencing odd behavior while using object snaps, the system is probably set to the System Settings method. The Line command is configured in this method by the program to automatically impose certain object snaps. The good news is that you can configure these system object snap controls, and you can switch back to total user control if you desire. Once you understand them, you will probably configure them to your taste and leave the System Settings on.

To find out which setting is being used for AutoCAD Mechanical object snaps, open the Options dialog box. My favorite method to access this dialog is to right-click on the Command line. Once there, navigate to the last tab to the right, which is labeled AM:Preferences. In the Snap Settings pull-down you will see which method is being currently used and how to change it. At this point, make sure it is on System Settings so we can see where the "automatic" object snaps came from.

The next selection will make a lot of users uneasy, because the settings are in code rather than a friendly dialog box. Take a deep breath and select the System button, which is located below the Snap Settings pull-down menu we just used. In the resulting dialog box, expand the two levels shown and highlight the Osmodes@Cmds entry. You have probably already guessed that this section controls the object snaps that are assigned to various program commands.

I need to present a short refresher lesson on how object snaps are assigned using the system variable OSMODE. If you type Sysvdlg at the Command line, you will see the System Variables dialog box. Select the OSMODE variable to display the possible numerical setting information. Please pay close attention to the text outlined in the graphic below on the method to assign more than one object snap mode. We will be using these numbers to set up the object snaps that are active when an AutoCAD Mechanical command is run.


AutoCAD Mechanical has three unique Power Snap Settings, shown below with their assigned system variable values.

Next, back in the System Editor, scroll down to the Line command on the Osmode4Cmds entry. The entry in my example is +39|4 but yours will probably be different. I believe a new installation of AutoCAD Mechanical has a value of -39.

The format for this value is as follows: Sign opt ACADSNAPMODES opt DELIMITER opt MCADSNAPMODES

  • Sign: The minus or plus sign. A minus sign makes the snap modes defined by ACADSNAPMODES or MCADSNAPMODES and those set in the Drafting Settings dialog box and Power Snap Settings dialog box active, when you use the respective AutoCAD command. A plus sign makes the snap modes defined by the ACADSNAPMODES or MCADSNAPMODES active, and disables those in the Drafting Settings dialog box and Power Snap Settings dialog box.
  • Opt: You can omit the following section.
  • ACADSNAPMODES: The value code for the AutoCAD object snap modes based on the AutoCAD "OSMODE" system variable.
  • DELIMITER: The pipe sign "|"
  • MCADSNAPMODES: The value code for the AutoCAD Mechanical object snaps modes: Arc Radial (1), Arc Tangent (2) and Symmetry (4).

The value is edited by right-clicking on the Key value and selecting Edit.

Using the above rules, the object snap settings (which automatically activate when you execute the Line command) will be Endpoint (1), Midpoint (2), Center (4), and Intersection (32) from the ACADSNAPMODES (39) and the Symmetry power snap from the MCADSNAPMODES (4). The plus preceding the number will turn off all other configured object snaps during the command, and turn them back on when the command is finished.


One last setting will help you monitor which object snaps are activated during the execution of various commands. In the Power Snap Settings dialog box, check the "Show snap in status line" option for all four Power Snap configurations.

When you select various commands the object snaps, either automatically or manually assigned, will appear in the status line.


About the Author: John Hackney

John Hackney

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