Fillet help?

Hey guys -
Hoping someone can shed some light on this. I’m trying to apply a .125" fillet on a solid. I’m using a telecaster (simple guitar body) as an exercise (file attached). The error I get is ‘failure in building corners’. I’ve added screenshots of the process:

I’ve read by way of a Google search that Rhino is notoriously poor at filleting, but I can’t help but think it’s more user error than a software issue.

I followed another tutorial for using the pipe command and then BlendSrf but ended up getting some pretty strange transitions around the neck pocket.

It seems like a fairly straight-forward action, but I just can’t get it to work. Any insight is appreciated. Here’s my process for the ‘pipe’ command:

I then used the split tool:

And then tried the ‘BlendSrf’ command:

And then here - no matter what options I choose, I’m unable to get the desired result:

Thanks in advance.TELE-EXERCISE-FILLET.3dm (3.6 MB)

Hello Mbhwhitney
If I was doing this, I would fillet before removing the neck housing. As it is, the filleting is always going to fail at those sharp corners where the neck will seat.

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Hi Tone -
Thanks a ton for replying. Your method worked; I applied the fillet before addressing the neck pocket and it came out as I hoped on the face and back edge.

I’m now faced with a new challenge: In the screenshot below, you can see the neck pocket I’ve extruded as a solid, .625". I’ve raised it above the body for visual reference:

I’ve attempted two methods to remove the pocket… a) with a Boolean difference, and b) using the ‘split’ tool, but neither are working:

The Boolean Difference method: ‘Boolean Difference Failed’

Split Tool: ‘One polysurface split into 7 pieces’

I then delete the 7 pieces one at a time and I’m left with the following:

You can see there’s a hollow cavity there now but I’m trying to create a simple pocket…

Are you able to shed some light on this?

Thanks in advance.

Hi Mike - make your cutter extend past the guitar body on the sides where the cut is low - that is, no sides…


Hi Pascal -
Thank you.

To clarify, do you mean like so…? If so, how do I extend the side as it currently tucks in behind the fillet. Is the goal to have a slight overlap to successfully execute the boolean difference command (or split function)?

Hello - yes - the idea is to avoid coincident faces in the inputs - planar ones will generally work but otherwise not. In this case it looks like you’ll want to make a slight L-shape. Keep in mind too that Boolean operations are a shortcut to trimming/splitting and joining - in some cases it’s simpler to just do that.


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Thanks Pascal.
I’ll give that a shot and report back. I really appreciate your advice.

Hey Pascal!
That worked - for the heck of it, I tried the Boolean difference after extending the curve beyond the body shape and extruding the planar curve. It may have worked to split > join as well, but I didn’t want to mess with a good thing. I’ll keep the latter in my back pocket should this method not work in future.

Feeling good; progress has been made; learned a few things… thank you again. I’ll post the photos in case it helps someone else down the road.

Hi Mike - nice to see that you are progressing on this one.

I just noticed these in your picture:

Those surfaces are way more complex than they need to be and should look something more like this:

Try to use simple lines and arcs where possible. I also noticed that they are slightly off from being symmetric. You can draw half of a shape and mirror that along the X-axis, for example.

Finally, some of the dimensions of features in that model are getting a bit too close to the document’s tolerance. The tolerance is not something that you should change midways into a project, though… Try to use significant decimals that are at least one order of magnitude larger than the document tolerance. So, instead of using a radius of e.g. 0.125, use 0.13 or work with the tolerance set to 0.0001.

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That is very dubious advice. I can’t think of any circumstance where that would do anything but make modeling more difficult. You can use radius with any number of significant digits after the decimal point. It won’t cause any modeling problems.

it is not a good idea to use a radius that is smaller than 10 times the file tolerance but that is not the same thing. A radius of .005 might cause problems but using a radius of 1.2567485367 won’t cause any problems (other than wearing out your keyboard faster)


Thank you for the tips, Wim.

Is there a quick way to simplify the complexity of the pickup cavities or is it easiest to just redo them.

If the latter is true, is it possible to fill the ‘hole’ left by the existing cavity as I redraw?

I found this line drawing online and will pay closer attention in future to symmetry and simplifying curves.


The command SimplifyCrv might do it if the shape of the curves you used are well within tolerance of true arcs and lines.

Untrim or DeleteHole should get rid of the hole(s). When you run either command you need to right click on the edge of the hole. If you don’t have the original curve geometry first duplicate the edge before getting rid of the holes.

Those are both good strategies

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When I create the curves for controlling 3d modeling I always just draw them myself. Working with imported curves is really asking for trouble as most lack proper structure, symmetry, end point continuity etc.

But sometimes I find it convenient to make a fast 2d layout using imported curves. Also I find Make2D from a solid model will often end up with tiny curves lying nearly on top of each other and generally the control point structure of many curves is really a mess.

First I SelAll and run SimplifyCrv to clean up the easy stuff. Then I weed out the micro lines with SelShortCrv, applying progressively larger tolerance until I start seeing small gaps. Then SelAll again and hit F10 to turn on the control point display. This will show me the problem areas that need manual attention. Sometimes I will rebuild the curve or simply replace it. Then I go through the drawing trying to join up or split the curves to find trouble spots. Sometimes I will manually grab an end point to snap it where it needs to go, etc.

It’s often easier to just draw the curves for an accurate 2D layout. Especially since I am usually producing a drawing that will be used to limit acceptable manufacturing tolerances. Even if my 3D model is accurate and can be used to generate the manufacturing files (CNC, laser, etc) we still still need 2D to communicate clearly. If the drawings are just for display it may not really matter.

Hope someone with better technical skills than mine can comment.

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Thanks @jim - I’ll give those a try (or just re-draw).

Deletehole worked perfectly, Jim - handy command!
I’m just going to re-draw the control and pickup cavities.
Thanks again.