OK, that title may seem a bit confusing. But what I am trying to do is simulate a custom cut endmill being swept through a helix.  However I get an error telling me my tool is concave and it must be convex.

Sorry for the old school ASCII style here, but this is essentially what my revolved tool looks like:

----          -----

|    \--------/     |

|                   |

|     /--------\    |

----          -----

And my helix that I am sweeping it through goes down through the middle of the coping.  What I am trying to make is a ramp cut into a tube with radiused surfaces top and bottom.  Again, using this tool doesn't work because it tells me it is concave. I tried just making it flat (which worked) but I wasn't sure how to get the entire surface to have a radius to it.  I also tried cutting the coped tool in half and mirroring it, then making a duplicate helix to follow (since it won't let me use one helix on multiple features). But this method completely blew up and had all kinds of funky things happen like incomplete cuts and solid being added into what seems like random locations.

In real life, this product is made by simply cutting a radius into an endmill then spinning the tube in the 4th axis as the part is pushed toward the tool (typical helix).

Any ideas?  Thanks.