Isodraft
Here’s a quick tip from the AutoCAD vault:
If you are working in cad and need to create a 2D isometric detail, AutoCAD has a feature called Isodraft which will help.
Isodraft modifies your cursor and 2D drawing plane to simulate a 3D isometric plane.
Here’s what you do:
Enter isodraft at the command line and choose one of the planes under options: Left, Top or Right
You can toggle between the planes using the F5 function key.
Enabling Orthomode (F8) will lock your line geometry to the 30 degree axis of the current plane.
You can draw to specific distances along the axis similar to othographic drawing.
If you need to draw an accurate isometric circle, you can use the Ellipse command.
Enter Ellipse in the command line and then enter “i” for isocircle. You can then draw an isometric circle in the current isoplane.
I had to use this recently on some flashing details and I found it very useful.