There is another problem: I haven’t condemned Rhino, but people are sure responding like it.
I know it’s better to revolve everything–including in this case, a revolved cylinder with a chamfer to subtract from my object, still I wished the chamfer result or its indication was better. Also, in this case, the process would have been subtracting two objects would have had them in a co-planer situation.
Have you looked at the result of the file I uploaded?