I previously mentioned [here] that the circle command with the TTT (tangent, tangent, tangent) option was only available with use of the ribbon. I am happy to report that there is a way around this in the form of an undocumented command called AI_CIRCTAN. There seems to be a bunch of commands that have that “AI_” prefix. I haven’t fiddled around with them to see if there are any gems. But when I do find some, I will post them here.
You can use this command and associate it with a button & macro and add it to a toolbar if you think that you will make use of it a lot. Again, this command is a deafult command with its own button in the ribbon found in the Home tab > Draw panel > Circle tool pulldown – Tan, Tan, Tan
Here’s how to use it:
- AI_CIRCTAN <enter> to start
- Select the 3 objects that you want the circle to be tangent to
~enjoy
AutoCAD Tips 
I have been doing this for a while by doing a circle -> 3 point and then using tangent o-snaps. is this different?
You are correct – this is not different. The only difference is that with this command/tool the tangent OSNAPs are set for you and you are ensured a tangential circle. I think that the most helpful point about this is that the user can use the undocumented command and make a button for the toolbar while they use the “AutoCAD Classic” workspace which doesn’t have this tool ready to be used as easily as in the ribbon.
Thanks you for pointing this out.
~Greg
Greg,
Would you happen to know why I cannot call this command from within an AutoLISP program? My program outputs the command to the command line, but AutoCAD then states that it is not recognized.
-Gnar (the N is mostly silent)