I am looking to make a hollow, filleted tube joint. I have made an outer and inner part (files attached). The outer part has 5 mm tube diamater, inner part has something smaller. Fillet radius on the outer part is 1 mm, and the fillet radius on the inner part adjusts accordingly to maintain constant wall thickness. I do Combine-Add on each of these parts. I then put them both into a part file (multipart file). I move them so that they are centred with one another. Then I try Combine-Subtract. (sometimes i add a little stub to the inner part so that i can select it weven when it is entirely encapsulated by the outer part). I have done this before, and it works great for smaller fillet radius. I am using "constant radius" fillet. The issue arises when I want larger wall thickness (therefore smaller inner diamter, therefore larger inner fillet radius). I get the error: Rebuild failed due to geometric conditions.

Why is this? I have noticed that "constant radius fillet" has more section per fillet then the radius is larger - for smaller radius fillets, the entire fillet is just one smooth piece. \

Ideas???

Thanks!