Filleting the interior edges breaks the object

In the process of trying to Boolean difference this part with another part and failing, I suspected that it no longer fully enclosed a volume and that I had broken the part in a previous operation. I decided to Multiple Undo in steps to find out at what point the object got non-fully closed.
I may be way off the beam, admittedly, but it no longer fully enclosed a volume after running FilletEdge on the interior edges.
Am I using the wrong command?
How can I fillet the interior edges without causing the part to no longer fully enclose a volume?
FilletEdge (84.5 KB)

Hi SaucerD - I think go back one more step before the fillets and MergeAllFaces, then FilletEdge.


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Oh no! I saved it before zipping it up so there’s nothing to undo!

Whether or not your model encloses a volume has nothing to do with whether booleans succeed or fail. That is just a superstitious belief. If you want to learn how Rhino really works you should learn how to use the surface modeling tools. By learning the solid tools you are not learning anything about how Rhino works.

Yes this is a very common occurrence when using filletedge.
Filletedge doesn’t like the breaks in your top surface. Since those surfaces are not planar the only way to fix it will be using the surface tools. First use extractSrf to extract all six of those surface and then delete all but one of them. Untrim the one surface you kept and then trim that surface and join it.

FilletEdge Woesx.3dm (204.8 KB)

Doesn’t matter, mergeAllFaces wouldn’t work anyway.

Hi SaucerD- the fillet will work if that curves front face is one surface - jim is correct that MergeAllFaces will not help here because that area is not planar, but trimming one surface from that big cylinder is the goal - then FilletEdge will finish the job - V5 still does not like tangent faces with an edge at the filleted corner- like you have it in the original - all separate little bits of the same cylinder coming together at the corner.
FilletEdge Woes_PG.3dm (575.1 KB)


Thanks all,

I rebuilt the object pretty much from scratch, did the FilletEdge operation before trimming and joining the cylindrical faces and that fixed it.
I appreciate the help.