Hi Jeff, that "Sharp corners" option will tell the fillet engine to not build corner patches in areas where several fillet surfaces are meeting at a juncture point. Instead of building corner patch pieces in those areas it will only intersect the fillets with each other.

In several kinds of situations the fillet surfaces may not actually intersect each other in a way that will allow a proper result to be made without any corner patches. There's an example of how this can happen when one fillet is on a concave area in the fillet help file topic here:
http://moi3d.com/2.0/docs/moi_command_reference7.htm#fillet

So anyway, that's not unusual that the sharp corners option will not be valid for cases where corner patches are needed to fill in what would be a hole created in the object.

However, it seems that I'm actually able to do the sharp corner fillet with your model - maybe some glitch in it was fixed up during saving and re-loading. But also the radius you mention 4.375 is way too large to fit on this model, did you actually mean 0.4375?

Here is what I get when filleting your posted file with a radius of 0.4375 and "Straight corners" enabled, does this behave better for you when loading back in this same file?



- Michael