Hi octo, I don't think you'd be able to do the fillet first before the chamfer because that would give you a result like this:



There you won't have the right topology to get the chamfer you want. Usually you have to apply larger features like a wide chamfer or fillet first before you apply a smaller radius fillet.

Yeah I guess it would be correct to say it's a technical problem with the fillet engine in the geometry library that MoI currently uses, it can sometimes have difficulty with this particular case of fillets meeting up across a sharp boundary with the surfaces being at different angles (90 degree angles is a special easier case). It's more difficult than it first appears because the correct result would look like this, note how the fillets are of different widths where they run into each other:



That's probably not exactly what you're expecting but it's how fillets in CAD programs are meant to work - the fillet surfaces there are all of a constant radius meaning they are arcs that are portions of the same radius circle but when the surfaces are at different angles to each other some will get a longer arc from that circle and some will get a shorter arc from that same radius circle.

The geometry library that MoI uses is not too robust in this particular situation but some other CAD programs can handle it better, you might check out OnShape or ViaCAD if you need to get that particular fillet done, the geometry libraries they use have been more highly developed for these kinds of fillet cases.

It is an area that I'm hoping to improve on in MoI in the future as well.

- Michael