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I'm using Boolean Modifier quite well so far, but this time I can't get it work properly. I guess it's sometihng I'm missing but I checked other answers for bolean modifiers and none of them seem to apply to my case. I have a concentric cylinder and a torus (I specify that they are concentric because if they are not concentric the modifier seems to work properly) I need to subtract the torus from the cylinder to create the housing for an O-Ring. The result are just more faces and vertexes added to the cylinder but the housing is not created. I checked normals and non-manifold but all seem to be ok. Anyone able to explain me what am I doing wrong? Sorry if duplicate, not able to find a proper answer.

Here an image that may explain the problem:

Problem explanation * My mistake: not "Binary mod" but "Boolean mod"

I hope it's clear what I wanted... instead of the same outer surface of the cylinder with more vertexes that you can see in the last picture I wanted a torus housing: a negative of the torus.

Here you can get my blend file

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    $\begingroup$ Hi. I suggest adding images to your question to illustrate your point. Ideally, we would prefer to be able to answer questions without having to download a blend file to diagnose the issue, unless it is absolutely required. Thanks. $\endgroup$
    – Ray Mairlot
    Commented Jan 14, 2020 at 16:10
  • $\begingroup$ Picture added. I hope it may help undertsanding the problem. $\endgroup$
    – Marco
    Commented Jan 14, 2020 at 16:27

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Boolean operators are known to have issues when dealing with complex interactions. Thus, it is advised to prep your meshes to minimize issues from the Boolean operator. This simply means giving the Boolean operator easy places to make cuts.

In your example, all you need to do is to add another torus with the same number of segments as the cylinder. This aligns all the torus edges to that of your cylinder, which eliminates the issue from the Boolean modifier.

Note how the wire-frames don't line up nicely in your torus, so the Boolean modifier will need to make a ton of cuts to try to modify the geometry.

enter image description here

I've added another torus below, this time matching the number of segments to the cylinder, and the boolean modifier works fine.

enter image description here enter image description here

Another thing to note: having an excessive amount of vertices in close proximity to one another can also cause problems with the Boolean modifier, but that's easily fixed by scaling/moving one of the objects slightly.

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    $\begingroup$ This solution as written by you was not solving my problem: with my torus of 17mm diameter and the cylinder of 17mm diameter the Boolean modifier was still not working. I needed to make a torus of 16.8 diameter to make it work. And if you look at your pictures the green torus created by you is in fact smaller than my red torus. A part from this thank you very much for your help! That led me to the solution and then absolutely appreciated! $\endgroup$
    – Marco
    Commented Jan 15, 2020 at 20:28

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