rotate your cylinder object 90 or 180 degrees in the back view before doing your work.

Thank you very much, I will try to follow your great tips!

Hi krass - I'm not entirely sure but I think that the problem might be a very slight (like maybe just 1 or 2 degrees) tangent difference between some of the large pieces. Even just a slightly sharp area means that fillets do not naturally have their ends aligned. When I do surface/surface filleting on those the fillet ends are just slightly off from each other and that usually should only happen on slightly creased things.

Either that or maybe some bug in filleting related to handling fillets that cross over the seam edge of a closed surface.

- Michael

Seems to be something going wrong with the fillet crossing over the closed surface seams.

I've attached a version here with those edges filleted at 0.5mm , I rotated the main tube 180 degrees in the Top view around its center point, to move the seam edge off to the other side where it does not run right through a small tube. After that I was able to make the fillets.

- Michael