Add Metal Threads to Your 3D Prints - Make Them Functional!





Introduction: Add Metal Threads to Your 3D Prints - Make Them Functional!

Connecting mechanical components can be a challenge with 3D printing. Tapping functional holes in plastic that can support a load is nearly impossible. I want to share an easy method I've found to add metal threads to a 3D print that you can do with just a soldering iron.

This Instructable is entered into the Full Spectrum Laser and Hack Your Day contests so if you think it's a winner for either one, I'd appreciate your vote! Thanks!

Step 1: Materials and Tools

You will need heat-set metal inserts for this. I purchased mine from McMaster-Carr.

The only tool you need is a soldering iron.

Step 2: Design Your Model

Your will have to have the right size holes on your model to fit the inserts. On McMaster, they list two tapered hole diameters. Find the sizes for your insert. The largest of the two is the diameter you will need to make your holes in your model. I usually oversize the holes in my models a little to accommodate for the 3D printer's tolerances. Mine usually prints holes smaller than they should be but yours may be different.

Step 3: Assembly

The next step is to 3D print your model. Once you've got your part made, then you can start assembly.

1. Heat soldering iron. Wait at least a minute for it to get hot. Remember to always be safe around heat!
2. While it is heating, you can position the inserts so that they rest on the holes.
3. Once the soldering iron is hot, place it inside the insert and push down gently.
4. As you are pushing, the insert will slowly sink into the plastic. You may have to wiggle the soldering iron back and forth to straighten the insert.
5. Continue applying pressure until the insert is flush with the plastic. Remove the iron from the insert.
6. Flip the part over and remove any extra plastic with a small knife or screwdriver.
7. Repeat for all other inserts.
8. Wait a few minutes at least before using the inserts to make sure the plastic is fully solidified.

The inserts will still be hot for a few minutes after so be careful not to touch them right away.

Step 4: Finished!

Now you've got some fully functional parts ready to go!



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In step 2 says to use the LARGER of the two dimensions for the hole size. That seems counter-intuitive as then there is no plastic to melt and hold the insert. The McMaster list is equally confusing about the process. Shouldn't the design's hole use the SMALLER dimension?

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The McMaster list isn't very clear on the matter. I used the larger of the holes when I made them and there was plenty of plastic to melt onto it with some that came out the other end. The tolerances on my 3D printer when printing holes seems to print them on the smaller size so I usually oversize my holes by at least 0.01". The smaller size would work too.

I find its easier sometimes to look at the CAD drawings on McMaster for clarification.

Hi, from what I understood from Mcmaster, and after I measured the insert, my guess would be that the holes have to be tapered, with the smaller diameter towards the tightening direction. Otherwise, I do not see much contact if the hole is straight.

Once the insert heats up, the plastic melts around the insert and when it solidifies it should hold the insert in place. If the hole is smaller than the insert, there will be extra plastic to remove at the end of the insert.

I wonder uf you could just bevel a brass nut with a grinder and make your own inserts...

1 reply

That would probably work. I would probably rough the sides with sandpaper so that the plastic has more surface area to bond to.

I've never needed an iron to use screws with my prints before. Does it make them more fixed or something? I'm now curious!

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Using the soldering iron on the inserts makes the plastic melt around it, making a super strong bond.

It may be good to know that the inserts are available with a larger diameter flange. This is helpful in the event that you could pull the threaded insert out of the plastic when tightening anything to it. My company learned that the hard way.

Hi - is that the recommended way to fit the inserts?? - if not then that is a very cool method - I don't use a 3D printer as yet ( no real need for one ) but any builds that could do with a solid thread will be getting your method shown here.
Great INST

3 replies

You can also leave the space to fit a normal nut which can be either glued or melted as above.

I've also left holes for nuts, put a pause in the gcode and stuck the nuts in and then 3D-printed over top of the nut (leaving the bolt hole). It's nice to have options.

Yes, that is the recommended method. McMaster sells special soldering iron tips for it but they aren't necessary.

ottima idea bravo. Così si risparmia tempo e lavoro

Thank you, fixed it. I oversize the holes a little because they print smaller, at least for me.

Ah that makes sense, I guess that depends on each person's printer. But it's definitely a good thing to include to get people thinking about how their particular printer prints. Thanks for the awesome tip, I have the McM page saved for the next time I need something like this.

This thing gives off fumes so do it outside OK

I have done this, I also found that having a 3d pen helps as you can weld the inserts in with it if you need