not entirely certain the shape you're aiming for, do you have a crude
drawing or picture of the off-the-shelf version?

On Sat, Dec 2, 2023, 22:08 Lee A via Discuss discuss@lists.openscad.org
wrote:

Is this any good to you Lee?

include <BOSL2/std.scad>
$fn = 128;

difference()
{
spiral_sweep(circle(5), h=90, r=20, turns=5);
translate([0,0,43])
cube([50,50,15],center=true);
translate([0,0,-43])
cube([50,50,15],center=true);
}

On 2023-12-03 16:37, Lee A via Discuss wrote:

--
Cheers, Ken
bats059@gmail.com
https://vk7krj.com
https://vk7krj.com/running.html

A baby can be defined as an ego with a noise at one end and a smell at the other.
Your job as parents is to teach them to control all three.
My job as a grandad is to tell you how you are doing it all wrong!

On 12/3/23 00:07, Lee A via Discuss wrote:

I needed a buttress thread so I made a small polygon describing the
tooth , extruded it o be about a degree thick, tilted it just enough the
steps in the thread pitch disappeared then looped it on the outside of a
cylinder to make a bolt. then to actually make the parts, if its being
used to difference() to make a nut, I make it a teeny bit bigger than
the printer nozzle, or if making a bolt I reduce the size by the same
amount.

Easier to describe than do but that is the outline. The whole thing is
around 45 mm in diameter but the shrink is only limited by the printers
definition and nozzle size. This is not brittle PLA territory, but PETG,
much more resilient.

Take care and stay well Lee.

Cheers, Gene Heskett.

"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.

• Louis D. Brandeis

On 12/2/2023 9:07 PM, Lee A via Discuss wrote:

Linear extrude with a twist seems like such an obvious way to make
threads or a helix... and it really doesn't work, if you want a round
cross-section.  It's possible to do, if you make a helix and slice it
and then extrude that slice, but that slice is hard to derive.  (It
looks sort of like a banana.)

Use a threads library.

https://github.com/BelfrySCAD/BOSL2/wiki/threading.scad
has a ton of technical details on how threads are designed, but the
examples are relatively simple.  Find an example that looks sort of like
what you want, and tweak it to your exact requirements.

The right sidebar lists a couple of specialized threading sub-libraries.

And threadlib of A Schlatter https://github.com/adrianschlatter/threadlib?

Ciao

Bruno Böttcher

35 rue de la république, FR-6720 Schwindratzheim
email: bboett@adlp.org, mobile:bboett@gmail.com
Fon:+33 3 88 89 91, Mob:+33 6 76 55 82 68

Dev: Java/Perl/PHP OS:GNU/LINUX, Android
Aïkido: http://aikido.zorn.free.fr, http://www.aikido-club-saverne.fr

Jordan Brown via Discuss discuss@lists.openscad.org schrieb am So., 3.
Dez. 2023, 08:22:

Hi Lee,

As others may or may not have said, a thread is a profile, which is
rotated and moved up or down a certain amount, usually an equal amount,
per rev, so to speak. A single  for loop can do that.

The profile can be generated by points on a polygon, or by combining
whatever shape you want, and it is linear extruded a small amount,
depending on what material and process you are using to create the
thread.  I then rotate that shape, and then rotate it and move
vertically in the desired direction and rate.It is easier to visualise
and create an external thread, and if you want internal threads, then
difference it from whatever object you want to be internally threaded.
Be aware of clearance, and the fact that many internal threads and
matching external thread do not have the same profiles.

I've attached the scad files that I  use. A Whitworth thread profile
example (whitprof.scad), and the file to generate a tapered plug. You
can adapt it to your needs if you wish. This tapered plug can take a
long time to process, but for a quick look, change the $fn value to
something smaller, However,  in the code attached, I've commented out
the lines that are not  not required so that a plain thread, with no
fancy ends is created.

Best wishes,

Ray

on 03/12/2023 05:07, Lee A via Discuss wrote: