How to use threaded inserts ?

Overview

Threaded inserts allow you to add durable, reusable metal threads to your 3D printed parts. This is essential for parts that need to be assembled/disassembled multiple times, or where strong screw connections are needed.

Note that threaded insert is a good solution but not the only one. A good practice is also to have a pocket in your design where you can simply put a nut inside.

This tutorial covers the process for heat-set threaded inserts and includes both design and installation instructions.

Step 1: Design the Hole in your CAD model

While modeling your part, design a hole at the insert location.
Use the exact hole dimensions provided by the insert manufacturer, like hole diameter (D3), depth (L) and minimal wall thickness (W) around the hole.

Tips:

Take some margin with the depth (at least 1mm more than the value)

Add a chamfer to help guide the insert in smoothly (0.3~0.5 mm)

Step 2: Print your part and check the hole fit

Once printed, try placing the smooth end of the insert (D2) into the hole by hand.
If it doesn't fit: Don’t force it! Ask your mechanical workshop coach for help using a precision drill bit to correct the hole diameter.

PET-G can shrink slightly after printing, so minor post-processing is normal.

Step 3: Place the insert by hand

Place the insert manually into the hole, starting with the smaller and smooth diameter end (D2).
It should sit snugly but not be forced in.
It only needs to start in the hole, not go all the way in — the heat will do the rest.

Step 4: Prepare the insert tool

Choose the correct tip size for your insert.
Mount the tip on your insert placement tool (while cold!).
Set the temperature to the printing temp of your filament: 230 °C for PET-G

Warning: This tool gets very hot. Always place it back on its stand when not in use.

Step 5: Heat-set the insert

Hold the heated tool vertically and gently press the insert.
Apply light, even pressure.
As the plastic heats up, the insert will begin to sink into the part.

Tips: Don’t force it — let heat do the work.

Keep the axis straight to avoid misalignment.

Watch the sides of the part — if it starts to bulge, stop. You may be overheating or pressing too hard.

Step 6: Make it flush

Once the insert is fully seated, you can use a flat metal tool to gently press it down, ensuring it's flush with the surface of the part.
This step helps with cosmetic finish and mechanical alignment.

You're Done!

Turn off your tool and let it cool down safely.
Don’t touch the metal tip — it remains hot for several minutes.

👏 Your insert is now permanently embedded and ready for screws! Don’t overtighten screws — inserts are strong, but the surrounding plastic can still deform.