From:  Michael Gibson
5022.9 In reply to 5022.4 
Hi Barbara - try using the Revolve command for building these kinds of circular type forms - Revolve will make much more precise and also lighter weight geometry for these kinds of things and that should avoid various problems.

It looks like in your case here you probably used Sweep along a circular path instead of Revolve? Sweep has a problem on some closed curves where it can make a surface that is not quite all the way smooth at the closure point, it can have something like a 1 or 2 degree deviation from being smooth right there. That kind of small shallow deviation then is something that fillet and chamfer don't like to deal with very well since fillet and chamfer surfaces do not meet up exactly at sharp juncture points and have to be extended and trimmed and also corner patches put in, all of that is difficult to handle for very shallow angle juncture points.

I am planning on tuning up Sweep for these cases to make a totally smooth surface result, but it's unfortunately not an easy fix, it's a problem in the geometry library.

But in the meantime if you use Revolve for this type of thing instead it should work better.

- Michael