<p>Hoping to get some help with something I'm trying to accomplish. Unfortunately, due to my being a noob with 3D modeling in general, I'm coming here for hopefully more direct help.</p>

<pre><code>Env. Details: OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13541 (Git)
Build type: Release
Branch: releases/FreeCAD-0-17
Hash: 9948ee4f1570df9216862a79705afb367b2c6ffb
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: English/UnitedStates (en_US)
</code></pre>

<p>Essentially, I have a need to design some housing for a small electornics board. Due to the nature of 3D printing being less than ideal for bending/snapping locks, I've decided to use small screws to hold multiple layers of housing together.
<a href="https://i.stack.imgur.com/CBSLA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CBSLA.png" alt="Placements to bore threaded holes"></a></p>

<p>SketchUp Free proved to be a super intuitive, easy to understand 3D modeling software, tho is limited in functionality due to paid tiers.
Unfortunately, FreeCAD felt like a confusing cross between early 2000s Microsoft Paint and Eclipse (Java). However as the open source alternative, I understand it's incredibly powerful and can/should be able to do what most 3D modeling software is capable of, if you know how to use it properly - and that's where my lack of understanding shines through. Research into my use case revealed a plugin (Fasteners Workbench) which seemed purpose built for dealing with screws/threads, and I greatly prefer this approach due to being able to select standardized sizes.</p>

<p>On to the problem:
I decided to sketch out the main design for the housing in Sketchup, and am happy with it, though I am missing the holes in the four corners. To add this, I decided to export the file from Sketchup as STL and import it to FreeCAD. Once in FreeCAD, I switched to the fasteners workbench and created a screwtap of arbitrary length. Now, from most tutorials I've watched, removing one piece from another is a boolean operation, often a cut or an intersection. However, when I highlight both the part object and the screwtap and select the CUT boolean operation, what I expect to happen (the screwtap was "cut" or carved out of the part object) did not.
<a href="https://i.stack.imgur.com/fWykE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fWykE.png" alt="Intersecting components selected, deciding on boolean operation"></a>
<a href="https://i.stack.imgur.com/BqkC7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BqkC7.png" alt="enter image description here"></a></p>

<p>I'm wondering if:
- My understanding of the boolean operation is wrong. There is a different function that is used for "boring" threaded holes?
- My process is wrong. Does exporting an STL from sketchup free not work for certain operations when importing to FreeCAD?
- My models are off. I have an understanding that "grouping" parts of models is big when putting a model together from parts, so as to simplify life. I'm wondering if it's also required in these cases? Attempting to do the boolean operation in sketchup failed but did require having grouped components. I'm not sure this is the case in FreeCAD, or if I'm already doing this?</p>

<p>Would appreciate any help with this. Attaching the FreeCAD file <a href="https://drive.google.com/file/d/17_NEe8SXjl54cQzKhfzkMZsMBHSc9e5X/view?usp=sharing" rel="nofollow noreferrer">here</a>.</p>

[{'answer_id': 13657, 'author': 'R.. GitHub STOP HELPING ICE', 'author_id': 11157, 'author_profile': 'https://3dprinting.stackexchange.com/users/11157', 'pm_score': 0, 'selected': False, 'text': '<p>In terms of Cura\'s model for showing overhangs, I\'m nearly sure it\'s just the ratio - rise over run, or rather run over rise. And indeed that\'s what makes sense mathematically:</p>\n\n<p>At least some portion of the wall extrusion in layer N+1 needs to sit on top of the corresponding wall extrusion in layer N. For a given 3D surface slope, the "run" - the distance the cross-section moves from one layer to the next, which needs to be bounded by some fraction of the line width - varies proportionally to the "rise" - the layer height.</p>\n'}, {'answer_id': 13659, 'author': 'FarO', 'author_id': 2338, 'author_profile': 'https://3dprinting.stackexchange.com/users/2338', 'pm_score': 1, 'selected': False, 'text': "<p>A wide line works if there is something below it to squeeze the filament against, but if you don't have a full layer below it, it will stay thinner and it will droop. I would not use extreme ratios on overhangs. Still, do a parametric test: a overhang tower (a compact one) at different line widths and layer heights. If you test 3 layer heights and 3 line widths, it's only 9 short prints.</p>\n<p>However, as you can see in filament reviews, different materials behave differently. I think there is no <em>a priori</em> optimal value.</p>\n"}, {'answer_id': 13875, 'author': 'woneill1701', 'author_id': 21453, 'author_profile': 'https://3dprinting.stackexchange.com/users/21453', 'pm_score': 1, 'selected': False, 'text': '<p>Cura high-lights overhangs in red if the printer would end up printing completely into thin air. </p>\n\n<p>If your overhang is angled instead of being a purely vertical-to-horizontal transition, a much thinner layer height can increase the chances that enough of the prior layer exists to support the next layer being printed. </p>\n\n<p>Basically, the thinner the layer (within reason), the greater the allowable angle of overhang that is safe to print.</p>\n'}]
['https://3dprinting.stackexchange.com/questions/13667', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/21212/']