Hi Steve - thanks for posting the examples!

Fillet has some problems on planar pieces that have seams or internal edges in them. That can be where there are multiple cut up co-planar bits joined together instead of one big plane, or in the case you show here where you've got a plane that is a kind of disc form with an internal seam.

In this case if you delete the top face, then select the object and use Construct/Planar to fill it with a simple trimmed plane that has no seam, then you can fillet up to the maximum amount of room.

For shapes like this where you're trying to sweep along a circular path, I would recommend using Revolve for that instead of either Sweep or Loft.

Revolve will produce a more simplified and precise result - the revolved result will fillet as expected without any extra work involved.


I'll take a look at the fillet failure in your example to see if there is anything simple that I can do to tune it up. But it is likely to be something that will need to wait until it gets fixed in the geometry library.

- Michael