Hi Bdaniel,

> That's great, got ya. Way simpler, but I would like to know why I can't fillet on those
> edges, just so I know for other projects.

It's because the surfaces that you were trying to fillet were already meeting up smoothly to one another - you can only apply fillets to edges where the surfaces are sharp where they come together at that edge.

Also when 2 surfaces approach very closely to being smooth but are only just barely not actually smooth that becomes a pretty difficult situation for the filleter to deal with, because part of the fillet calculation involves doing an offset of the surfaces and then an intersection between those and 2 surfaces that meet at a shallow angle usually have more of a sort of "area of overlap" rather than distinct clear intersection curve between them. Filleting needs to find a clear intersection as part of its calculations.

Also 2 surfaces that touch sharply along most of their common area but are smooth just at one end are also difficult for the filleter to handle as well, that's a "disappearing fillet" situation where the fillet starts to get tinier and tinier as it approaches the smooth area and evaporates to a single point at the actual smooth spot, the fillet engine that MoI uses is not very good at handling those kinds of fillet situations either.

- Michael