Recessed Surface

Looking for help.

I have a simple solid that I’m trying to add a recessed area with filleted corners, to represent a milled out area, cut perpendicular to the surface

I can get the recessed area easily enough by doing a boolean difference with a solid formed from offset surface, but when I attempt to add the fillet it fails at the junction of the flat and radiused surfaces. When the fillet command runs, it leaves a discontinuity on the inner surface corner that prevents a watertight surface from being formed.

Any suggestion as to what to try differently.

Recessed Fillet Edge.3dm (943.9 KB)



Hi Paul,

The reason FilletEdge failed was due to a discontinuity in the ‘pocket’ surfaces around the area where it failed. So that’s a matter of how the pocket was made to make that smoother, but to fix it after the fact I first just did what I normally do and used FilletSrf to create the necessary fillet to fill in the bad area with manual surface editing. Then I realized you had the construction geometry so I also went back to redo the FilletEdge to see what the origin of the issue was, and as a quick fix I simply added the edge that wasn’t tangent to the edges to fillet and it worked.

Recessed Fillet Edge.3dm (741.8 KB)


Thank you. I appreciate the fix, but I’m sorry I don’t follow how you got there as you removed all your construction lines, and I don’t follow your steps, particularly for the one without the additional surfaces.

Did you start from my un-filleted recess?

How did you get the recessed surface to be trimmed without any discontinuity?



With the one on the left I started with your final result. I Extracted the fillet and other surfaces around the problem area, used FilletSrf to make the ‘missing’ fillet surface–I had to extend or Untrim one of the surfaces to get the full needed surface–and then trimmed and joined things all back up. Yes that’s putting it a bit generally. FilletSrf is in fact how I do MOST of my filleting these days, it can be be faster and more useful in form-finding than farting around trying to set up the model to FilletEdge properly without issues like this to troubleshoot.

On the one on the right I went back to before your FilletEdge. When I did the FilletEdge I included the problematic edge that’s not tangent in the edges to fillet–perpendicular to the original fillet. That let the fillet work.