From:  Michael Gibson
2048.18 In reply to 2048.12 
Hi Brian, no problem. I'm sorry that filleting gives so much trouble it is unfortunately a quite sensitive and complex calculation involved with it.

It looks like PaQ has given some great steps above there for how to make a more totally "fillet friendly" shape.

I took a look at your model, and it actually your existing model seems to fillet ok for me at a small radius value like radius of 0.2 .

So after doing that, here is a look at that front edge that PaQ was referring to:

Zooming in:

You can see there that since those pieces do not meet smoothly, it forces the filleter to try and splice in a kind of corner connection piece between them. Making those smooth to one another will eliminate that and helps makes a more simple fillet structure there, that can help.

Then the other thing is notice how this "seam" edge is pretty close here:

Probably the #1 problem with fillets currently is that it will not cross a nearby edge like that, it will only approach it. So currently it tends to be best to make your part actually cut through the seam instead of come close to it, that avoids that issue.

- Michael