Hi Duke,

I think it's this edge that you want to fillet? :




If you zoom in on that circled area, there is kind of a nexus of small edges in that area:




That's not good for filleting - basically the fillet will be limited so that it must be small enough so that it does not hit any of those pieces. So basically you don't want these edges in there really at all:




It is possible to kind of bypass those edges by doing what is called a surface/surface fillet which is a slightly different way to fillet. That can be activated by using Edit/Separate on your model to break it apart into individual surfaces and then picking 2 surfaces at a time and doing Fillet. That type of fillet is not so sensitive anymore to edge structures and is built more directly following along surfaces instead of edges.

However, it can be less convenient than the edge-based one because the edge-based one knows how to build corner patches where different fillets intersect. With the surface/surface one you can need to do some more manual trimming and handling of corners where pieces meet. But in this particular case it could actually work without much fuss, here is what it looks like using surface/surface fillet to build some fillet pieces:




Again, that is by using Edit/Separate, then picking pieces 2 at a time and running Fillet. That good part about that is it would let you finish that fillet without doing any reconstruction at all I think...

When you first create that kind of stuff, try to have pieces that extend more all the way through each other and let the edges be create when they are booleaned with each other, if possible - that createes more simple edge topology. Edge filleting can't really handle complex junctures of many edges coming together very well.

- Michael