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Does anyone know where I can get a free 3D design (STEP or STL) of an M4 Screw and nut? I have found only an M3 on Thingiverse: M3 Bolt by Kaleta.

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You can get a model for nearly everything McMaster-Carr sells from their website.

M4 Hex Head Screw - https://www.mcmaster.com/#91280a140/=15dmpx8

M4 Nut - https://www.mcmaster.com/#90592a090/=15dmqjy

The options to download models are to the right of the drawings.


NOTE: the site does prohibit use of these models for direct printing.

You shall not use a CAD model to engage in 3D printing or other fabrication of the object depicted in the CAD model for any other purpose. You shall not otherwise redistribute or make available the CAD models (or any design drawings or prototypes that incorporate them) to any third parties, including third parties in the business of selling products similar to the products sold by us.

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The thing you linked to describes itself as being generated from a parametric model: http://www.thingiverse.com/apps/customizer/run?thing_id=193647

To generate any different bolt or nut, you will need to identify the correct dimensions for not only the thread (where hints exist in the customiser), but also for the hex head. These are obviously less critical to define than the thread.

Once you have generated a custom model, you can share it and answer your own question.

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  • $\begingroup$ Actually, I think that the owner of the linked item created the matching customizer page. You need to start w/ a SCAD dwg before you can create a Customizer, so far as I know. PLease add info correcting me if I got this wrong. $\endgroup$ Dec 8, 2016 at 14:34
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A 3D printer does not have the necessary resolution to create a functioning screw thread. I suggest you print the hole (for the nut) and the shaft (for the screw) in oversize and use a tap and die set to make the threads.

You must print them out of PA12 nylon obviously. Due to the size, warping will not be an issue.

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    $\begingroup$ Maybe you should add that this is true for smaller thread sizes, I've printed larger threads that worked fine. SLS can even have a higher resolution. $\endgroup$
    – 0scar
    Jan 30, 2023 at 10:46
  • $\begingroup$ I've printed an M36 once, so yes. But as long as you can cut the thread, you should cut it, not print it. $\endgroup$
    – AzulShiva
    Jan 30, 2023 at 10:47
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You could also apply a scaling factor in your slicer to make a downloaded object larger or smaller. An M3 model scaled at +1.333 would produce a working thread with a nominal 4 mm OD. As noted in the comments below, a different scale factor might be needed in the axial direction if exactly matching the pitch of an M4 thread is required.

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    $\begingroup$ That's not true. You'll want to scale it with a factor of 1.33333 along the thickness of the screw, but a factor of 1.4 along the length of the screw. Please study this chart and fix your answer: carrlane.com/engineering-resources/technical-information/… The threads of an M4 screw are 0.7mm apart. The threads of an M3 screw are 0.5mm apart. The threads of an M8 screw are 1.25mm apart. So an M3 to M4 scales 4/3th along it's width and 7/5th along it's length. $\endgroup$
    – AzulShiva
    Jan 30, 2023 at 21:40
  • $\begingroup$ It's true that the thread resulting from scaling all three axes at 1.333 would not exactly match the pitch of a standard M4 thread. It would, however, produce a working set of threads as long as both male and female components were scaled at the same factor. If attempting to make a true M4 part to mate up with a standard M4 component it would be necessary to apply a different scaling factor in the axial direction to duplicate the standard M4 pitch. $\endgroup$
    – allardjd
    Jan 31, 2023 at 14:10

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