I’m using Grasshopper to create some fillets and I identified what looks to be a fairly simple fillet which was unsuccessful. I know that I can trim away the excess to resolve the issue, but to avoid this error in the future I would love to know why this fillet is failing at 2-3mm. I am getting the same result in Rhino, Why is this fillet unsuccessful? (3DM attached)
Before
After
Failed fillet.3dm (222.8 KB)
after extending the surfaces and retrimming, and joining the surfaces back into a solid, the fillet succeeds:
Hi Gigs,
Thanks for your thorough reply. I’ve cut this section (the 3dm in my original post) out of a larger model which I unfortunately can’t share here. I am referencing a mesh to make a custom-fit component and rebuild some curves. I have traced back through my grasshopper process and I have identified the source of the 10-degree curve. I used 10 degrees as it gave me the best-looking curve for my needs. Clearly, this is not the correct approach. Would you mind explaining to me why this is so and guiding me on the best practices for a situation like this? Thank you 
10DegCrv.gh (12.3 KB)
So does the fillet succeed normally if you rebuild to a more regular degree, eg 3 or 5?
I don’t think investigating just the curve is going to provide much info as to why you get bad trimming tolerances.
Hi Gigs,
Thanks, reducing the degree to 5 has fixed the issue. Thanks so much. I am self-taught and have some holes in my knowledge. I appreciate you taking the time to review my issue. Have a great day 
