About this video
What Are Heat-Set Inserts and Why Use Them?
Heat-set inserts are small metal threaded bushings that melt into a 3D printed part, creating strong, reusable threads. Instead of tapping directly into plastic, you embed a brass or stainless insert so screws can be tightened and removed repeatedly without stripping the print. This is the go-to method for anyone who wants their 3D printed parts to stop feeling cheap and start feeling like a finished product.
Step 1: Size the Hole Correctly
The most important step is getting the hole diameter right. Find the outer diameter of the heat-set insert, then design the hole 0.4 mm smaller than that measurement. This extra material gives the insert something to bite into and prevents it from spinning or pulling out under load.
- In CAD software: model a cylinder subtraction at the exact target diameter.
- In your slicer: use a cylinder primitive as a negative shape to cut the hole directly on the print bed.
Step 2: Heat the Soldering Iron
Set your soldering iron to printing temperature for your filament:
- PLA: around 200 °C
- PETG: around 230 °C
- ABS: around 250 °C
A temperature-controlled soldering station works best. Too cold and the insert won't sink; too hot and you'll melt through the surrounding plastic.
Step 3: Press the Insert In
Place the insert into the hole, then slowly and steadily push the soldering iron tip into the insert. The heat transfers through the metal and melts the plastic below. Apply gentle, even pressure until the insert is flush with the surface.
Step 4: Level It While Hot
Before the plastic cools, press the part flat against a table or a hard, level surface. This ensures the insert sits perfectly flush, which is critical for mating parts to align cleanly.
Pro Tips for Premium Results
- Use a soldering tip that matches the insert diameter for even heat transfer.
- Add a small chamfer or countersink to the hole top to help guide the insert.
- For high-stress parts, print the surrounding area at higher wall count (4–6 perimeters) to give the insert more material to grip.
- Let the part cool completely before inserting a screw to avoid warping.
FAQ
Can you add inserts to any filament?
Yes, but PLA and PETG work best. ABS and ASA also work well at higher temperatures.
What if the insert spins after installation?
The hole was likely too large. Re-melt and remove, then redesign with a smaller diameter.
Do I need a special soldering tip?
A tip slightly smaller than the insert inner diameter gives the best contact and cleanest result.
