Fillet issue


I am quite new to Rhino, I love it and such an easy learning curve… There’s just one thing I keep struggling with, Fillets, often I manage to fix it with workarounds but never actually know why it sometimes work and why sometimes not. I’ve attached a file with my current fillet error. Would love to know why this doesn’t work and what solution is the most efficient (need to repeat this quite a lot.)

Thanks in advance.

I noticed that the problem seems to be due to the side being made of four rectangular surfaces. FilletEdge will work if you create one surface on the side using the Surface => Planar Curves method. I’m not sure why this works though, but it does :smile:

This trick can’t be done with the small hole in the middle of your object though. There you can use Patch or EdgeSrf to fill the hole.

Thanks Menno, deleted the side surfaces, used cap planar holes and then the fillet worked perfect! Many thanks for this solution!

Hi Philippe,

There a few things I always think about with fillets that might help you as you learn.

  • Always fillet from the largest radius to the smallest radius across a model.
  • Remove any edges you can prior to filleting with MergeAllFaces or by way of surfacing in a simpler manner. Less intersected edges = less problems as the fillet rolls along any edges and tries to trim and join with the adjacent surfaces.
  • Make sure there is enough room for the fillet surface to trim and join with adjacent surfaces. The angle relationships between surfaces, sharpness of the bend in the rail around corners and rail type all play a part in any particular case.

Here are two video tutorials as well which may be of use.