@hunter first of all the inside of the screw is too straight on, needs to be at more of an angle. Also, add more sides, don't just do a square, it helps to have at least some sides in there, I usually use a 6 or 8 sides for round objects, depending on size. Iterations won't solve everything for you.
also, your edges should look more like this, supporting edges are important.
That's probably not perfect either, but the two edges surrounding the outside and inner circle are
Bookmarks