Full Version: How to extend a screw thread?

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re:
> I tried to copy and paste the thread but cannot get it to match up perfectly.

It's because this data isn't the original accurate CAD model, the model you have here is a triangulated approximation.

Do you have any specs on it like what is the pitch supposed to be?

- Michael

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How accurate do you need it to be?

I estimated a pitch of 1.25 mm and just tried to eyeball the profile to make this attached version.

This was done using the method in the above links, with a helix path and a profile curve to sweep:





The result of the sweep is used as a cutting object in boolean difference against a cylinder:



- Michael

Attachments:
20mm_bolt2_3dm.zip

Image Attachments:
extended_thread1.png  extended_thread2.png  extended_thread3.png 

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It could be more accurate (and easier to make) if stuff like pitch, profile shape, radius, center point were given in a spec instead of trying to reverse engineer all of those from the triangle soup.

- Michael

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Hi Michael,

Thanks for taking the time to have a look. I don't have any specs on this at all. The file was included in a 3d printing job. I had to modify a part to be larger which resulted in the screw being too short. Yours looks extremely close so I will try and do a test print to see if it fits. :)

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Image Attachments:
Screen Shot 2025-05-20 at 4.15.53 PM.png  Screen Shot 2025-05-20 at 4.16.27 PM.png 

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Those Images are from one blender Tool that allow to make good aprox.

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"""""""""""""" I don't have any specs on this at all. The file was included in a 3d printing job. I had to modify a part to be larger which resulted in the screw being too short. """"""""""""""

Since you dont have any of the thread specs and the original prinyt and model were most likely modeled to fit, I woud approach your modification a little different

I would add a cylinder at the ID size of the threads to the part between the head and existing threads. Just need to be sure that the tensile integrity that will be slightly less, is ok with that method...

I will look at your model then attempt to separate the head and threads and make a bridge of 8mm in a poly modeling app.

I'll update later...

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Hey Bean,
So I ended up just doing this in MoI. I separated the threads from the head and created the 8mm gap, then i ended up with 2 solids.

I can put a "Pin" cylinder in between the 2 solids and Boolean it in to create a printable object. The pin should be smaller than the id of the threads to allow the threads to go deeper like you want,

A picture to illustrate. Your file back with 2 solids allows you to define your own "Peg/Pin" to extend the threads up.

Image Attachments:
seperation peg added.jpg  seperation peg.jpg 

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Here is the file. You'll have to let me know if you cant access it. Not a google drive user....

https://drive.google.com/file/d/1DddrzDzhtq9FL7keVJE2YqL7vaNyHouX/view?usp=sharing

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