How to fillet this surface?

Hi guys,
I’ve modeled this in Solidworks. I want to try Rhino’s filleting performance and I want to fillet the edge which has been marked in the image below by a fillet radius larger then the surrounding fillets (by 2 or 3). The fillet fails and I want to know how can I fillet it manually. What is the procedure for manual filleting? (I should mention that Solid works can do this so easily and in seconds but I want to try Rhino)
Please guide me. Thanks
Untitled.3dm (1.1 MB)

surfaces created in one application might cause problems in others. i think it would be best to start and finish an object in the same application, meaning if you want to test rhinos performance then you should start the object there. filleting over an existing fillet can also be pretty tricky not only in rhino and probably even more if it was created by another application. in this shape generally you might have to avoid the rolling ball option because of the upwards warped bottom. maybe it would involve some manual trimming.

1 Like

The question arises spontaneously: “If you started modeling with Solidworks why you did not run the fillets with the same modeler?” Conducting fittings with Rhino is not the best choice: too many limitations!

1 Like

Best is, for intricate filleting, to use Creo or SolidWorks. Fillets with Rhino are tricky and cumbersome. Best is to knock up complex shapes in Rhino, because that’s cumbersome in SolidWorks, but do all filleting in SolidWorks. That’s how most design studios I know do it also. Saves an endless amount of time.


Hi Alex

Here is how I’d do that using fillets only, no blends or patches etc.
I mean, using FilletSrf, that is working with surfaces.
First I ran 0.5 fillets on the marked edges, extended them where needed,
then ran the 0.2 fillets on the 0.5 fillets.
Last I trimmed away the parts to discard …Eeeh, I have to say this is the hardest part (for me at least),
Often I had to use borders or borders extended on surfaces to be able to trim …
( I hope someone will tell us how to do this more easily … )
Finally you can Join again the surfaces to get a solid … actually here a few naked edges remained … maybe my fault …

AlexWright-1.3dm (3.3 MB)

I think it would be interesting seeing SolidWorks’ result :slight_smile:


Same… if there was extendneededsurfacetotrim that would be nice. maybe like Alt+Click for extending surfaces to trim.

1 Like

Don’t know for solidworks, But Fusion 360 do the job in a second.

Fillet-Fusion360.3dm (1.1 MB)

Nice !

I was curious to see if the surfaces were different …
Exactly the same surfaces Rhino does ( with FilletSrf etc. )

Thank you !

1 Like

Your trimming problem is due to the fact that often you have to zoom in and use setpt to get the pointy end of the fillet to land at the point where the 2 bigger fillet edges intersect. Often the fillets do not quite reach the point of intersection as you can see if you zoom in (use a parallel view)

I generally avoid pointy ended fillets as much as possible. They are the number one CAD problem for manufacturers. They often cause file translation errors between CAD programs and they often cause machining and other manufacturing problems.

There is really no reason for the pointy fillets to exist. If you zoom in to that little triangle that is missing in your model you will see that the triangle is dead flat and can easily be filled with
a planar surface. The fillet could be cut back even farther and the hole would still be flat to within tolerance and a planar surface at that point will be a lot more robust than a singularity.

In the enclosed file I made the pointy ended fillets just to show that Rhino can do it, but I would never do that if this were my model. The little cyan surface is how I usually handle pointed fillets, but the red fillet joined to a trimmed planar surface would work fine also
Large fillet after small.3dm (605.3 KB)


The Rhino filletsrf surfaces are actually better than the Fusion surfaces, but your trim boundaries are a mess.

Here is one corner of your model trimmed cleanly. with the point part replaced, If you offset those individual surfaces by one unit you will get an idea of how much better the Rhino fillets are than the Fusion ones (comparing the same surfaces the same way)
offset_This.3dm (62.1 KB)

The superior accuracy and excellent tangent continuity of the FilletSrf fillets makes a huge difference when you have complicated models with lots of overlapping layers of fillets.

Hi Jim

Yes, me too, I usually try to draw shapes that don’t need that.
… But sometimes I have to use some of them.
I also have a script that looks for pointy surfaces and tries to cut away a little piece at the point edge. :smile:
Usually I don’t care about very small holes, but know that offsetting a pointy surface can be … a little dangerous. :wink: , so I try to avoid it.

Didn’t know about using SetPt though …

Very valuable info as usual from you. :slight_smile:

Thank you !

When using FilletSfr, I usually then trim by the fillet surface(s) or by its edge ( possibly extended ) …

What should I do to build better edges ?

One thing you should do is turn on CheckNewObjects then Rhino will alert you to some of the bad edges as they are created, Also it helps to work in parallel viewport so that you can zoom in and see what is going on.

When a fillet comes to a point is a special case that usually needs special handling
The example file I sent in the last post shows how I would deal with the special case where the usual methods fail offset_This.3dm (62.1 KB)

Those fillets came from your file. All I did was used SplitSrf to trim back the pointy end of the fillet a little and then drew 3 straight lines to define a small rectangle. The 3 lines plus the existing fillet edges can be used to trim everything cleanly. Then that little rectangle can be filled with just about any surface creation tool. EdbeSrf, planarsrf, loft, sweep2 – just about anything will work. I often use blendSrf.

The important thing to understand is that the fillets get wonky where all the surfaces are essentially flat.

Large fillet after small.3dm (2.2 MB)
Is this the area you were asking about filleting? I used Jim’s model to look at.
I also am learning something about fillets today .thanks ,Mark

A variable radius fillet is an excellent way to avoid the pointy fillets. Nicely done.

Its too bad Rhino’s variable fillet surface can’t make good variable radius fillets that work to make those surfaces.

And it’s a lot of manual work… I think (maybe I’m wrong) that the original poster wanted to know, if one can simply add the large fillets later, after the small fillets are in place already, like in SolidWorks. And that’s not possible as far as I know. But then, I might have missed a sort of hidden tool.

Understood. :slight_smile:

Thanks again for your help.


1 Like

Yes, something to tell Rhino: ‘extend, join, etc. , but please, just trim this damned thing !’ :wink:
Trimming is the single operation that makes me waste more time.
( Although I use several custom scripts for that )