Hey all, having another problem with a new project. 

I went over my old thread from a couple months ago where I was looking for help turning a 2D drawing, into a 3D object so I could add more elements (such as counter boring, etc.). With that project, I was able to get the drawing working and had the piece CNC cut with success.

I can't seem to find the fault in my drawing to turn it into a 3D ring with holes in it.

I feel like the inner and/or outer borders must not be properly joined somewhere, but when selected they each say they are closed.

When I select all the elements and try to EXTRUE them to a 3D object, the whole centre extrudes as well.

What am I missing!?

I've attached a screen shot of the drawing, but also the .dwg file if anyone is willing to open it up and have a look at it. 

There must be something I'm doing wrong once again, or just simply over looking.