Chordal fillets with minimum radius?

I’m trying to get used to Rhino having different names for everything than the rest of the industry…

(Like “Fillet Edge” is apparently a G1 radius fillet, while a “Blend Edge” is a G2 fillet.)

Now… “Rolling ball”… is that a chordal fillet or not? I suspect it is in most cases, because tube offsets was what we used 15 years ago when normal fillets failed, but I believe chord width calculation is more exact, so is there a way to get such a fillet specifically?

Further, is there a way to get a chordal fillet with a minimum radius option?

I’m referencing this page currently:

inside the fillet options you have RailType = RollingBall , if you click there you have also DistFromEdge and DistbetweenRails which is the chordal fillet

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Hmm… where, exactly, is that?

In the FilletSrf, I only see Radius, Extend and Trim.

In the FilletEdge, I only see ShowRadius, NextRadius, ChainEdge, FaceEdges Preview and Edit.

Also, is there a “minimum radius” option hiding there somewhere?

I don’t think so, what’s the function of that option?

Minimum radius measures the curvature surface of a G2 fillet and ensures that it’s not too tight at any point, if you for example need to mill the part you’re designing.

In Alias, it suggests a minimum chord length depending on the minimum radius you want to achieve (it’s quite a heavy operation since it needs to measure the preview fillet at every point).

the Railtype option shows up once you have done selecting edges.
the min radius option is under the surface analysis tools

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Thank you!

you welcome

I tried to use this function now, but I need help with how to interpret the results:

Why is the blue fillet at the bottom apparently 0 after hitting Auto Range?

It’s a FilletEdge with a size of 2mm using the DistanceBetweenRails option, and the walls are at an 88 degree angle…

chord.3dm (631.4 KB)

I think is because it have planar surfaces which have inifinite radius or something like that. I guess you have to set the range you want to analyze.


Hello- for min radius, it may be more useful to set numbers than use the auto - for example, 1.6 max and 1.3 min will show you that fillet’s range of radii is pretty much right in the middle.

What Diego said…



@DiegoKrause @pascal

Thank you both for the super quick answers! :clap:

I understand now. :+1:

btw is there a tool or somethig to get numeric results instead of color gradient @pascal ?
some sort of dots or something on the surfaces?

Diego, actually I think do have a thing that may help… let me have a look around.

@DiegoKrause - This can probably use some work but it might help - for instance as is, it only accepts surfaces, not brep faces - that should be easy enough to fix but it tells me I probably thrashed this out fairly quickly for some immediate task. At any rate it reports back max and min radius at the pick point and leaves a point object named accordingly so you can go back later. (759 Bytes)
To use the Python script use RunPythonScript, or a macro:

_-RunPythonScript "Full path to py file inside double-quotes"


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