ThreadProfile now with multi-start threads

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TheMarkster
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Posts: 5505
Joined: Thu Apr 05, 2018 1:53 am

ThreadProfile now with multi-start threads

Post by TheMarkster »

I've just updated ThreadProfile workbench to support 2-start and 3-start v threads. I also added a 45 degree variant that should be more 3D printer friendly when printing without support. To use these create the standard v thread profile and then change the Variants property to select the other alternatives.

They have a lot of seamlines, but check out in checkgeometry. If you want a good rendering which to shaded view in the view tab for the sweep object.

Standard 60 degree v thread:
Snip macro screenshot-eb6bce.png
Snip macro screenshot-eb6bce.png (82.39 KiB) Viewed 10061 times
45 degree variant:
Snip macro screenshot-80e28d.png
Snip macro screenshot-80e28d.png (55.29 KiB) Viewed 10061 times
2-start variant:
Snip macro screenshot-45534d.png
Snip macro screenshot-45534d.png (104.45 KiB) Viewed 10061 times
3-start variant:
Snip macro screenshot-87acf3.png
Snip macro screenshot-87acf3.png (112.2 KiB) Viewed 10061 times
Cadder
Posts: 46
Joined: Sat Sep 03, 2022 6:52 am

Re: ThreadProfile now with multi-start threads

Post by Cadder »

Hi,

what exact relationship between major and minor diameters? Assuming we choose preset M10 Fine 1.0mm external:
Capture.JPG
Capture.JPG (18.8 KiB) Viewed 7322 times
Minor diameter is 8.77, and real major diameter is 9.88:
Capture.JPG
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I tried to calculate minor according to

Code: Select all

        def cd(txt, tpi, nominal): #cd = calculate diameters
            pitch = 25.4/tpi
            length_of_engagement = 10 * pitch #10 * pitch, longer engagements should have more tolerance
            nom = nominal * 25.4
            minor = nom - 0.66271 * pitch
            tolerance = 0.002 * (nom)**(1/3) + .00278 * length_of_engagement**(1/2) + 0.00854 * pitch**(1/2)
            return[txt, pitch, minor - tolerance, minor + tolerance]
 
And got following numbers:
Capture.JPG
Capture.JPG (42.84 KiB) Viewed 7322 times
So the question is how exactly diameters calculated? Assuming we have rod with some predefined non-standard diameter, how could we fit threading? The same for internal thread.

Also when switching from 60 deg to 45 real outer diameter decreases. How could we fit threading to rod diameter?

Thanks.
Hannibal
Posts: 28
Joined: Tue Aug 20, 2019 5:56 pm

Re: ThreadProfile now with multi-start threads

Post by Hannibal »

Hi,
is it posible to add 55° for Whitworth threats?
https://de.wikipedia.org/wiki/Whitworth ... ewinde.jpg
I sadly dont have the skills to insert one.

Armo
TheMarkster
Veteran
Posts: 5505
Joined: Thu Apr 05, 2018 1:53 am

Re: ThreadProfile now with multi-start threads

Post by TheMarkster »

New version 1.88. I fixed a bug that was causing the sweeps to fail check geometry with bop check enabled. The problem is actually in FreeCAD or possibly OCCT. The new Helix SegmentLength property was producing bad sweeps if SegmentLength is set to 0 (the default). This property makes for helices with a single edge rather than the segmented edges in previous version. It looks great, but produces bad outcomes. My workaround is to set Segment Length to 1.0.

Hopefully, this fixes the issue.
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