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I'm trying to connect two 3D printed parts (ABS) together with a threaded connection. Thus, I need to fix a threaded metal nut (M4) inside a corresponding slot which I've implemented in the design.

Right now I apply a conventional super glue on the nut and press it inside the print, wait for a couple of hours and then use it.

Problem is that the nut keeps falling out of the print when I apply a more tension to the bolt. Can you please advise me on how to make this method work. Maybe some of you aware of special glue for that purposes?

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3 Answers 3

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One good option would be to - if possible - change the design, so the nut is inserted from the opposite side, so that the bolt just pulls it in tighter rather than pulling it out.

Another option would be to instead of using a nut, use a brass threaded insert. These are like nuts, except they have ridges that are specifically aimed at locking it inside the plastic.

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  • $\begingroup$ huh! that's smart!! )) $\endgroup$
    – LoomyBear
    May 16, 2017 at 15:26
  • $\begingroup$ There are a larger variety of threaded inserts - not just brass. Just note that for maximum hold, make sure that you insert them from the opposite side from where you will insert the screw, If you are going to press them in then I would recommend the ultrasonic ones. $\endgroup$
    – markshancock
    Jun 4, 2017 at 2:54
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Instead of super glue, you could try a two part epoxy resin (any brand should do, i.e. Bison Kombi Power or JB Weld). This may take longer to dry, than the super glue, but should be much stronger, and deal with torsion forces better1.

Or, you could try red (not blue) Loctite. However, the epoxy resin would probably be stronger.

1 This is admittedly an opinionated reference, but from Epoxy or super glue, which is stronger?

depending on the surface, [epoxy] can be superior. Epoxies are generally a must if the surfaces are porous

and

Epoxy is superior to CA. CA is nearly always misapplied. Epoxy has a higher tolerance to misapplication thus is much less likely to fail under such circumstances. I've used Belzona epoxies to repair parts on various aircraft and spacecraft where welding would be inappropriate! Belzona epoxy is without a doubt the best there is. Too bad you cannot purchase it in Home Depot.

The closest thing you can get though is PC-7.

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Just heat the nut with a soldering iron to seat it into place (after the print). I've done this many times myself.

EDIT: Try a bit of acetone, to allow the ABS near the nut to reflow.

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  • $\begingroup$ Yeah! I know that trick. I do it before I glue the nut inside. But it goes out anyway :/ $\endgroup$
    – LoomyBear
    May 16, 2017 at 14:47
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    $\begingroup$ Oh. Have you tried a little bit of acetone instead of glue? To melt the ABS? $\endgroup$
    – Davo
    May 16, 2017 at 14:49

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