http://www.anim8or.com/smf/index.php?action=dlattach;topic=4378.0;attach=10897;image
Give the software Anim8or a shot.
It may not be CAD-accurate design, and it IS geared towards modelling (even while sporting a moniker like Anim8or), but I like to think it holds its own in the free software world.
I made an account, I'll have to try it sometime.
Here's that image, for those who want to see without making an account:
