Pictures would be helpful to see what you are trying to do.
Or an example file......
There are no good tools in SolidWorks to accomplish this. People who do this use other CAD tools and import them.
The geometry works, GW3D, add-in has this function. visit cadcamcomponents.com and ask for a demo.
I have not used it yet. I use the GW3D conic surfaces with beautiful results.