Extrude the arc and then use the THICKEN command?

Can you supply a dwg file?

Without knowing what your path looks like or what form your arc takes I tried a little experiment of my own.

I drew three paths.  The first was a straight line.  The second was a slight arc and the third was a polyline that I used the "fit curve" option on. 

Next I drew a small arc, offset it 0.06, connected the ends of the two arcs with a line segment then used the Pedit command > Join option to make it a continuous polyline.

I Used the Extrude command > Path option and extruded this arc along all three paths without any problem.  All three extrusions were identified as 3D solids with the List command.

So it can be done.  The thing we need to do now is figure out what went wrong with your attempt.

uploads/20110922_234656_Extruded_Arc.dwg

DWG file was saved to 2007 file format.


Edited by John Connor - 22.Sep.2011 at 23:48

The fact you did not have a solid and the arc was hollow inside leads me to believe that you extruded plain lines and ended up with surfaces.  Glad to hear that you got it to work the second time around.