There’s a variety of ways to add threaded holes to 3D printed objects. You can tap a hole, but the plastic isn’t always strong enough. Nut traps work, but aren’t very attractive and can be difficult to get exactly the right size. If you try to enclose them, you have to add a manual step to your printing process, too. You can buy threaded inserts (see video below) but that means some other piece of hardware to have to stock in your shop.

[PeterM13] had a different idea: Cut a piece of threaded stock, put nuts on the end and heat it up to let the nuts reform the plastic. This way the nut traps wind up the perfect size by definition. He used two nuts aligned and secured with thread locker. Then he used a hot air gun to only heat the metal (so as to reduce the chance of deforming the actual part). Once it was hot (about 15 seconds) he pulled the nuts into the open hole, where it melted the plastic which grips the nuts once cooled again.

Once in place, you could remove the threaded stock or use it as part of the assembly. Once you remove the displaced plastic, the result is a good-looking nut trap. If your metal/plastic fusion dreams run more to the electronic, you might consider printing these.

This is one of those clever little tricks that is so simple you want to smack your forehead for not thinking of it first. Thanks for sharing!

Cool idea! Might consider using “coupling nuts” (sounds NSFW but it’s OK (really!)): https://en.wikipedia.org/wiki/Coupling_nut

For a long time I had used coupling nuts and all thread epoxied onto caps for my Z axis rods to make a brace/hanger between the two rods. The caps had filament guides in them.

There’s also rivet nuts that you simply press into a pre-drilled hole, preferably with glue:

http://www.yihanfastener.com/wp-content/uploads/2011/11/RIVET-NUT.jpg

Another version called the split body rivet nut is designed to expand into the hole when you tighten it.

http://www.normandyfasteners.co.uk/images/steel_blind_rivet_nuts/Steel-Blind-Rivet-Nut5.jpg

https://www.enfasco.com/atlas-fasteners.php

I use these inserts – they work great and easy to use. You can use an epoxy to seal them in.

http://www.grainger.com/category/rivet-nuts/thread-insert/fasteners/ecatalog/N-8o5

I use these. they work fantastic and are really easy to use in a lot of ways. I have epoxied them in, etc…

I’ve been doing this for years with acrylic and other plastics. He didn’t cut a piece of threaded stock, it’s just a brass threaded insert for plastic. They usually have knurled edges and I have always used a soldering iron to push them in.

I think you are looking at the video. The link is to an article where [PeterM13] improvised with some all thread, two nuts, some clamps, and a hot air gun.

this video doesn’t match the text at all. What gives?

You have to see the part of the text that says:

You can buy threaded inserts (see video below) but that means

Threading / tapping PLA usually works well for me. Or gluing in the nuts with 302 2K 5 min. glue. Works great with PLA and ABS. But this gives you nice, reliable threads – if you need to use the thread more than 10 times it is a good way to go. To optimize it I would maybe use an aluminum or copper screw and heat that to have better control of the alignment of the screw. If you really need to fasten something very tight, an additional hex nut does the trick – it spreads the pressure and before the thread fails the part fails.

I have those cool taps from Harbor Freight that are at the shank end of the right size drill bit. So you put the thing in your drill, bzzzzz, and you come out with a tapped hole. With ABS and PLA you don’t even really need cutting oil. I’ve had good luck with this too, but the strength is not always good enough.

I love those. They hold really well, and as of yet, I haven’t had a part I’ve threaded using them break.

This is the item in question. Not sure it would be good for metal, but they are absolutely great with PLA. http://www.harborfreight.com/metric-drill-tap-deburr-bit-set-95529.html

Yep, that’s the ones.

METRIC?! I take it you aren’t in the states? I guess if you buy all your hardware off of ebay or other internet sites you’d be ok.

Woops, my bad. They make an SAE set too. I think I still like a regular tap anyway. You can buy them in bulk packs of the usual sizes and throw them out after a few runs. Old taps will bite you, even with cutting fluid or wax.

But that makes little sense for 3D printed objects, because you already printed your core-hole. So tapping alone is sufficient if you use the correct core-Ø from wikipedia. Tapping a solid part is not really a good option because you might have loose filling in there, while core-holes always get the print’s wall-thicknes and that is usually sufficient for tapping.

PRO-TIP for those users planning or buying tapping-gear: There are two kinds of tappers: single-pass and 3-pass. For aluminum and plastics single-pass is great. For steel you might want to consider 3-pass :-)

Then there are two sub-categories: For through-holes and pocket-holes. #1 has a gradually widening tap-cutter, so that you start with an unfinished thread and while driving the drill in it widens the thread. This means it is a little forgiving when starting the thread, but also that you have to screw it through all the way and even more to finish your tapping. #2 Starts with the end-diameter at the very tip so you are able to get a thread right to the bottom of your pocket-hole. This kind is harder to use since you have to make sure to get the right angle for the thread from the start.

Yes if I’m using those I do not put a hole in and I’m printing fairly solid, or I put a small hole in place. Like I said, not always strong enough but it just depends on what you are doing.

The downside to doing this is that unless you print a very dense part you will have very little material holding the nut in place. With a nut trap the slicer will add additional material underneath, above and on the sides of the nut, strengthening the location it is in.

I use T-nuts in wood cases, I haven’t tried them in my printed cases yet, but they should work fine using the same method referenced in this post. The added benefit of the spike of the T-nut is that it would add more contact surface area. https://en.m.wikipedia.org/wiki/T_nut

I’m glad somebody shared this, I’ve used a variation on this for situations where thread strength is not critical but wiggle room would be problematic. I have the slicer do an extra perimeter layer and design a plain hole into the part, then once it is printed I heat a machine screw up with a hot air gun and simply screw it in place and then back it out a quarter turn every 5 seconds or so as it cools. Using this trick I have been able to screw things to the part and have them stay firmly anchored. It works great with PLA but I have not tried it with other plastics.

I bet a wingnut would hold pretty well in large parts.

Note, instead of using a heat gun, with PLA, you can put the metal bits in boiling water. 100C will be enough to get PLA soft, but not liquid, and thus perfect for inserting tightly fitting stuff.

THAT is smart thinking! *missing a LIKE-button…*

These http://www.mcmaster.com/#standard-threaded-inserts/=yqyokr

Damn, no edits. The McM shortcuts are weird it won’t link to the specific product category. I meant to link to all the sizes of this style insert: http://www.mcmaster.com/#92398a116/=yqyx1l

Werner was doing this a year ago:

https://youtu.be/iGNXHWPFAKo?t=70

I usually add a slot and then slide the nut in from the side. YMMV.

Blast from the past: http://hackaday.com/2015/03/06/diy-thermal-insert-press/

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