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I'm new to blender and using it to create 3d objects for my printer. Part of this is "cutting" holes for bolts very precisely which I managed to do but my way is so long/tedious I must be missing something.

Here are my steps which I am illustrating with an imaginary use case I created for proper step-by-step exposure of my method.

My bold head is 0.8m radius (1.6m diameter) and 0.5m height.The thread of the bold is 0.6 radius (1.2m diameter) and infinite lenght. I'm cutting this hole in the center of the "top" face of the default 2m cube.

So here are my steps:

  1. I am creating two curve>circle in object mode with respective radius of 0.8 and 0.6 for the bolt head/thread. I precisely position them where I want (here, at the center 0,0) enter image description here
  2. I then select both circles and the cube, go in edit mode and mesh>knife project (cut through). enter image description here
  3. I delete the "top" round faces and extrude the bottom Annulus (apparently that's how it's called) 1.5 meter (since 0.5m is my bold head height). enter image description here
  4. Since I extruded it, the "bottom face" has gone up and it's missing in bottom position. enter image description here
  5. So I select every edge as shown below and "bride edge loop" them. enter image description here enter image description here
  6. Now I need to create the faces for the bolt head housing so I do a similar operation (select every edge as shown below and "bride edge loop" them). enter image description here enter image description here
  7. Then I check with the 3D printing extension and I have 96 Non-Manifold edges. enter image description here

  8. Thanks to What is non-manifold geometry? I realize it's because of internal faces so I tediously delete all the edges constituting the internal faces. enter image description here

  9. I then get the result below but checking again with the "Check all" 3D printing extension I have 96 bad contig. edges. enter image description here

  10. But this time the "Make Manifold" auto-resolve is working for me so it's finally good. enter image description here

At this point, I've spend a lot of time for what I would expect to be a simple task, how would you do it in a faster/simpler way ?

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I'd do it almost your way, just skipping a couple of steps..

enter image description here

  • As you did, knife Project and cut through
  • Deselect the bottom faces, and E extrude the top faces downard, numerically entering the depth of 0.5 in the 'last operator' panel
  • Select the top and bottom inner faces, and..
  • ...'Bridge Edge Loops' (you don't need to delete)

However, if your topology is simple enough to stand it, and you wouldn't need to do too much tidying afterwards.. you could just make and duplicate the bolts in the correct dimensions, and cut them all out in a single boolean operation.

enter image description here

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    $\begingroup$ Great answer, I have had a lot of issues when I was beginning Blender with Booleans leaving "dirty" (unprintable) meshes so I have been trying to never do them but it works great with a bolt difference ( But I need to have higher head since the perfectly aligned surface will not boolean-difference well, I understand why you made higher heads on your second picture after trying it). $\endgroup$
    – shrimpdrake
    Apr 11, 2019 at 20:37
  • $\begingroup$ @shrimpdrake I'm allergic to Booleans myself... but.. if you've got 100 bolts to put in... Yes.. Booleans ( in any application) can't deal with coincident faces. They've got to know what's inside, and what's outside. $\endgroup$
    – Robin Betts ♦
    Apr 11, 2019 at 22:21
  • $\begingroup$ ..the other advantage is that the Boolean (as a modifier) is non-destructive. You can move the holes, if you change your mind. $\endgroup$
    – Robin Betts ♦
    Apr 11, 2019 at 22:33

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