How to install heat-set threaded inserts in 3D-printed RC parts

Every MMC chassis is held together with M3 brass threaded inserts melted into the printed parts: 97 in the XP2, 85 in the XP1 and 96 in the D3. They give the plastic a metal thread that survives being screwed and unscrewed many times. Getting them in straight is the first skill of any MMC build.

The manuals use two sizes:

Part number	Insert	Used in
TI-4	M3, 4 mm long, 4.5 mm outer diameter	XP1, XP2
TI-6	M3, 6 mm long, 4.5 mm outer diameter	XP1, XP2, D3

The tool

A basic soldering iron is enough; it doesn’t need to be a fancy one. Very cheap ones from AliExpress do the job.

What matters is the tip: it should be fairly thick, so it can push an M3 insert in properly.

The trick for perfectly square inserts

When the insert goes into a flat face of the part:

1. Push the insert in with the iron, but stop a few tenths of a millimetre short, leaving it slightly proud.
2. While it is still hot, flip the part over onto a flat surface.
3. Press the part down. The flat surface finishes pushing the insert in, flush and perfectly square with the face.

Fixing a crooked insert

Reheat it slightly, without overdoing it, and move it straight while the plastic around it is soft.

Where they go

Each step of the XP2 and XP1 build guides lists the inserts it needs, numbered on the drawing, and most sub-assemblies start with “Install the threaded inserts”. The D3 build guide has the full parts list.