Screws with a pitch greater than 0.243 inch

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Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Screws with a pitch greater than 0.243 inch

Post by Frotz »

I'm trying to model a wooden screw of 1-inch diameter with 4 TPI, which translates to 0.25-inch pitch. When I create such a screw with the Fasteners workbench, I saw where the threads would go, but the cuts didn't get made. Playing around with this, I discovered that the greatest pitch I could get was 0.245-inch. Going to 0.246-inch would give me the wacky non-threading. What's going on?

Below is a screenshot of a 1-inch diameter rod threaded at a pitch of 0.245 on the top and 0.246 at the bottom:
badscrew.png
badscrew.png (173.21 KiB) Viewed 831 times

Code: Select all

OS: Debian GNU/Linux 11 (bullseye) (MATE/mate)
Word size of FreeCAD: 64-bit
Version: 0.21.31189 (Git)
Build type: Unknown
Branch: master
Hash: 2131a4732b00a65aeac0d3366db575df50c00364
Python 3.9.2, Qt 5.15.2, Coin 4.0.0, Vtk 7.1.1, OCC 7.5.1
Locale: English/United States (en_US)
Installed mods: 
  * Assembly3 0.11.3
  * Pyramids-and-Polyhedrons
  * sheetmetal 0.2.58
  * freecad.gears 1.0.0
  * A2plus 0.4.60b
  * fasteners 0.4.23
  * Manipulator 1.4.9
Attachments
badthreads.FCStd
(978.53 KiB) Downloaded 15 times
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: Screws with a pitch greater than 0.243 inch

Post by chrisb »

Sorry for not answering your question, but for a wooden thread I would rather use a trepezoidal shape for the thread and thus do it manually with a helix.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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Shalmeneser
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Posts: 9474
Joined: Wed Dec 23, 2020 12:04 am
Location: Fr

Re: Screws with a pitch greater than 0.243 inch

Post by Shalmeneser »

Same problem (a recent Fastener wb is needed. an old one breaks when recomputed)

Code: Select all

OS: Windows 10 Version 1909
Word size of FreeCAD: 64-bit
Version: 0.21.30265 (Git)
Build type: Release
Branch: master
Hash: c35244e74f326a04c5bcab31e984742db582ac78
Python 3.10.6, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.2
Locale: French/France (fr_FR)
Installed mods: 
  * fasteners 0.4.25
  * sheetmetal 0.2.59
Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Re: Screws with a pitch greater than 0.243 inch

Post by Frotz »

Shalmeneser wrote: Wed Dec 07, 2022 10:20 am Same problem (a recent Fastener wb is needed. an old one breaks when recomputed)

Code: Select all

OS: Windows 10 Version 1909
Word size of FreeCAD: 64-bit
Version: 0.21.30265 (Git)
Build type: Release
Branch: master
Hash: c35244e74f326a04c5bcab31e984742db582ac78
Python 3.10.6, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.2
Locale: French/France (fr_FR)
Installed mods: 
  * fasteners 0.4.25
  * sheetmetal 0.2.59
I updated the Fasteners WB and now when I specify a pitch of 0.25-inch straight away, I get an error of

Code: Select all

<Part> ViewProviderExt.cpp(1267): Cannot compute Inventor representation for the shape of Unnamed#ThreadedRod: Bnd_Box is void
Specifying a pitch of 0.245 and 0.246 give me the same problems as I described before. Interestingly, if I increase the screw's diameter to 2 inches, a pitch of 0.25 is accepted. The maximum pitch for that was 0.491.
badthread2.png
badthread2.png (155.47 KiB) Viewed 694 times

Code: Select all

OS: Debian GNU/Linux 11 (bullseye) (MATE/mate)
Word size of FreeCAD: 64-bit
Version: 0.21.31189 (Git)
Build type: Unknown
Branch: master
Hash: 2131a4732b00a65aeac0d3366db575df50c00364
Python 3.9.2, Qt 5.15.2, Coin 4.0.0, Vtk 7.1.1, OCC 7.5.1
Locale: English/United States (en_US)
Installed mods: 
  * Assembly3 0.11.4
  * Pyramids-and-Polyhedrons
  * sheetmetal 0.2.59
  * freecad.gears 1.0.0
  * A2plus 0.4.60f
  * fasteners 0.4.25
  * Manipulator 1.4.9
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Roy_043
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Posts: 8450
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Re: Screws with a pitch greater than 0.243 inch

Post by Roy_043 »

There have been update issues with the Fasteners workbench. In some case you first have to manually delete the Fasteners installation folder.
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papyblaise
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Location: France

Re: Screws with a pitch greater than 0.243 inch

Post by papyblaise »

wooden 6x80
Attachments
6x80 à bois.JPG
6x80 à bois.JPG (14.96 KiB) Viewed 583 times
6x80 à bois.FCStd
(568.44 KiB) Downloaded 9 times
Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Re: Screws with a pitch greater than 0.243 inch

Post by Frotz »

papyblaise wrote: Thu Dec 08, 2022 1:33 pm wooden 6x80
I'm sorry. The kind of screw I'm trying to model is a wooden rod with threads cut into it -- not a metal screw intended for driving into wood. I'll keep this sample in mind because I've wanted to model wood screws now and then, but have so far just ignored them in my modeling.
Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Re: Screws with a pitch greater than 0.243 inch

Post by Frotz »

chrisb wrote: Wed Dec 07, 2022 9:42 am Sorry for not answering your question, but for a wooden thread I would rather use a trepezoidal shape for the thread and thus do it manually with a helix.
I figured that the threads generated by the Fasteners workbench would be close enough for my purposes since I was planning to use an off-the-shelf tap and die designed for wood.
Frotz
Posts: 105
Joined: Thu Jun 21, 2018 1:52 am

Re: Screws with a pitch greater than 0.243 inch

Post by Frotz »

Roy_043 wrote: Thu Dec 08, 2022 9:29 am There have been update issues with the Fasteners workbench. In some case you first have to manually delete the Fasteners installation folder.
Done:
badthread3.png
badthread3.png (177.99 KiB) Viewed 450 times
chrisb
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Posts: 53920
Joined: Tue Mar 17, 2015 9:14 am

Re: Screws with a pitch greater than 0.243 inch

Post by chrisb »

Frotz wrote: Sat Dec 10, 2022 2:22 am I figured that the threads generated by the Fasteners workbench would be close enough for my purposes since I was planning to use an off-the-shelf tap and die designed for wood.
That means, that the thread is used mainly for cosmetic reasons. In that case you may have a look at the Thread for Screw Tutorial, with different suggestions for fake screws. They are way more efficient, which can be significant with big models.
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