Fillet for a narrow corner

I want to have that round fillet inside and outside of my model with the fillet command but it seems like one corner (photo No2) is to narrow. so the fillet can’t go around it. What should I do? Any suggestions?

Hi Sia - you’ll need to either do this ‘by hand’ maybe with some trimming and Sweep1, or, make your object hard-cornered to begin with - that is, leave the triangle un-filleted, and add all the edge filleting at the end, with variable radius if needed on the tapered corners. I’ll make some examples, hang on a bit.

@Siavash - here’s a file with a couple of examples - one show how you might fix the existing fillets (btw, make sure, when you Sweep1 on that one, that ‘Refit rail’ is set in the Sweep1 dialog). The other shows it done with the tapers in the fillet process. I do not love how Rhino chooses to make the corners in this case, so I replaced one corners with a new Sweep1.

FilletTaperedCorner.3dm (231.0 KB)



Pascal! you’re a genius!! Thanks so much! That was fast and very accurate!

Hi Pascal, I needed to do some very similar corner filleting recently and ended up using Sweep 2. I tried Sweep 1 and the results didn’t look anywhere near tangent. I had a quick look at the file you did for Siavash and the Sweep 1 corners seemed to suffer from the same problem - they don’t look tangent at all (still much better than Rhino’s automatic effort). Is this just a graphics issue or are they actually not tangent?

Out of curiosity, will Rhino 6 be able to handle this kind of fillet?