[OpenSCAD] Creating screw threads?

[MichaelAtOz]

Bump - so it goes to the mailing list.



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[Robert Rapplea]

Try this. It's simplistic, but you should be able to adjust it to do what you're
looking for.



linear_extrude(h=20, twist=20*90)

{

union()

{

circle(r=15);

polygon([[30,0],[7.5813,13],[7.5813,-13]]);

polygon([[-30,0],[-7.5813,13],[-7.5813,-13]]);

}

}

Post by MichaelAtOz
Bump - so it goes to the mailing list.
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The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/
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[Chow Loong Jin]

Post by Robert Rapplea
Try this. It's simplistic, but you should be able to adjust it to do what
you're looking for.
linear_extrude(h=20, twist=20*90)
{
union()
{
circle(r=15);
polygon([[30,0],[7.5813,13],[7.5813,-13]]);
polygon([[-30,0],[-7.5813,13],[-7.5813,-13]]);
}
}

If you can plot out a polygon of the thread profile for the entire length of
rotation in a circular form, you can then linear_extrude it with a certain
amount of twist and height in order to get your screw.

Basically, take a thread profile, plot it on graph paper on an X/Y axis, and
change the X/Y labels to angle/radius, and you've gotten a proper cross-section
for your thread.

I implemented this in https://github.com/openscad/MCAD, in fasteners/thread.scad
in the dev branch.

[Chow Loong Jin]

Post by Chow Loong Jin
[...]
If you can plot out a polygon of the thread profile for the entire length of
rotation in a circular form, you can then linear_extrude it with a certain
amount of twist and height in order to get your screw.
Basically, take a thread profile, plot it on graph paper on an X/Y axis, and
change the X/Y labels to angle/radius, and you've gotten a proper cross-section
for your thread.
I implemented this in https://github.com/openscad/MCAD, in fasteners/thread.scad
in the dev branch.

https://github.com/openscad/MCAD/blob/dev/fasteners/threads.scad#L147 for a
generic trapezoidal thread that can generate buttress, acme, and metric threads.
Doing a tapered thread this way is beyond me, though. I'm thinking of replacing
this approach with the sweep() module from the list comprehension demos, which
would be cleaner and simpler to implement.

[MichaelAtOz]

have a look in libraries/mcad/screw.scad and search thingiverse.com for
'screw'.



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Unless specifically shown otherwise above, my contribution is in the Public Domain; To the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. This work is published globally via the internet. :) Inclusion of works of previous authors is not included in the above.

The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/
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