Updated: Thread for screw tutorial

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vocx
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Updated: Thread for screw tutorial

Postby vocx » Sat Mar 28, 2020 7:48 pm

I updated the Thread for Screw Tutorial in the wiki for v0.19.

This tutorial was originally made with v0.14, and I think it assumed use of the Part Workbench only.

I added more information about the process using the PartDesign Workbench, and better images.

I did not touch significantly the methods 4 and 5 because the instructions they contain are a bit hard to follow in my opinion. So I would have to investigate exactly what they mean, and then re-write them.

I add in this post the files that I used to generate the models and the images. I will reference this post in the wiki as well.
T13_Threads_01_fake_threads.FCStd
(90.72 KiB) Downloaded 59 times
T13_Threads_02_real_helical_threads_small.FCStd
(840.79 KiB) Downloaded 57 times
T13_Threads_03_real_helical_threads_Part.FCStd
(151.85 KiB) Downloaded 49 times
T13_Threads_04_flat_images.FCStd
(59.6 KiB) Downloaded 42 times
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chrisb
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Re: Updated: Thread for screw tutorial

Postby chrisb » Sat Mar 28, 2020 9:23 pm

vocx wrote:
Sat Mar 28, 2020 7:48 pm
T13_Threads_02_real_helical_threads_small.FCStd
We often recommend to minimize the number of dimensional constraints, so I propose this sketch for the section:
Snip macro screenshot-a2eb76.png
Snip macro screenshot-a2eb76.png (7.69 KiB) Viewed 1308 times
It has the additional advantage that it shows directly the important angle of 60° and omitting the obsolete construction line.
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jruiz
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Re: Updated: Thread for screw tutorial

Postby jruiz » Sat Apr 04, 2020 1:31 pm

I think that in Thread for Screw Tutorial, the
Method 3. Sweeping a vertical profile
should be complemented explaining how to cut the thread so that no abrupt ends appears.
Furthermore, instead of using Part WB for creating the inner cylinder, Part Design WB should be used.
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chrisb
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Re: Updated: Thread for screw tutorial

Postby chrisb » Sat Apr 04, 2020 1:49 pm

jruiz wrote:
Sat Apr 04, 2020 1:31 pm
I think that in Thread for Screw Tutorial, the
Method 3. Sweeping a vertical profile
should be complemented explaining how to cut the thread so that no abrupt ends appears.
+1

Furthermore, instead of using Part WB for creating the inner cylinder, Part Design WB should be used.
There is nothing said how threads have to be made using PartDesign. So either it has to be explained in full detail or only the principles should be shown; thats how it is now.
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jruiz
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Re: Updated: Thread for screw tutorial

Postby jruiz » Sat Apr 04, 2020 1:54 pm

chrisb wrote:
Sat Mar 28, 2020 9:23 pm
vocx wrote:
Sat Mar 28, 2020 7:48 pm
T13_Threads_02_real_helical_threads_small.FCStd
We often recommend to minimize the number of dimensional constraints, so I propose this sketch for the section:
Snip macro screenshot-a2eb76.png
It has the additional advantage that it shows directly the important angle of 60° and omitting the obsolete construction line.
Don't know how about, but sometimes I get unwanted behavior from FreeCAD when using previous profile.
For example, the profile shown in threadProfile.png has worked fine for me.
In the image, the arrows point the difference between the two profiles.
Attachments
threadProfile.png
threadProfile.png (24.45 KiB) Viewed 1184 times
Last edited by jruiz on Sat Apr 04, 2020 2:18 pm, edited 2 times in total.
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jruiz
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Re: Updated: Thread for screw tutorial

Postby jruiz » Sat Apr 04, 2020 2:06 pm

chrisb wrote:
Sat Apr 04, 2020 1:49 pm
There is nothing said how threads have to be made using PartDesign. So either it has to be explained in full detail or only the principles should be shown; thats how it is now.
A simple way I found for cuting the ends of the thread is using a groove:
Attachments
1.png
1.png (210.95 KiB) Viewed 1186 times
2.png
2.png (263.42 KiB) Viewed 1186 times
3.png
3.png (253.74 KiB) Viewed 1189 times
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jruiz
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(Errors when submiting)

Postby jruiz » Sat Apr 04, 2020 2:15 pm

.
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Re: Updated: Thread for screw tutorial

Postby jruiz » Sat Apr 04, 2020 2:25 pm

Another way of cutting up the thread I like best:
Attachments
Captura de pantalla de 2020-04-04 10-21-11.png
Captura de pantalla de 2020-04-04 10-21-11.png (194.76 KiB) Viewed 1181 times
Captura de pantalla de 2020-04-04 10-21-21.png
Captura de pantalla de 2020-04-04 10-21-21.png (220.62 KiB) Viewed 1181 times
Captura de pantalla de 2020-04-04 10-21-32.png
Captura de pantalla de 2020-04-04 10-21-32.png (385.43 KiB) Viewed 1181 times
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chrisb
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Re: Updated: Thread for screw tutorial

Postby chrisb » Sat Apr 04, 2020 4:42 pm

I guess that real life bolts have neither of these, they rather have a 45° chamfer.

It may also be worth a discussion whether in PartDesign additive or subtractive sweeps are better. Most sweeps I see in PartDesign use subtractive. Together with the chamfer that seems to be easier than the additive variant.

Another topic is the inner runout in a partially threaded bolt like the Fasteners ISO4014 bolts.
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Snip macro screenshot-72a167.png
Snip macro screenshot-72a167.png (19.6 KiB) Viewed 1155 times
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jruiz
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Re: Updated: Thread for screw tutorial

Postby jruiz » Sat Apr 04, 2020 9:33 pm

chrisb wrote:
Sat Apr 04, 2020 4:42 pm
I guess that real life bolts have neither of these, they rather have a 45° chamfer.
Ok.
Attachments
1-4.png
1-4.png (517.76 KiB) Viewed 1137 times
5-8.png
5-8.png (461.95 KiB) Viewed 1137 times
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