fails difference boolean

 From:  jbshorty
Hi all. Just to point out one potential problem - If you do use the scaling method to fix the problem, it would be better to scale a little bigger (1.001) than to scale smaller (.999). Because if you scale smaller you will create some very thin surfaces and edges that might cause problems later for a fillet and when exporting to mesh. The best solution is to fix the original profile circle as Michael mentioned, and then sweep a new toroidal object.