What temperature should I use for heat-set inserts?

The common rule is 10 to 20 °C above the material print temperature: around 225 °C for PLA, 245 °C for PETG, 265 °C for ABS and about 280 °C for nylon.

Which soldering iron should I use?

Any temperature-controlled iron works. What matters is fitting a press tip matched to the insert bore rather than using a normal soldering tip, and keeping the iron vertical, which is what a press does for you.

What happens if the iron is too hot?

The plastic melts too freely, the insert sinks too deep, and a ring of molten material squeezes up around the boss, leaving it weaker. If you see that ring, drop 10 °C and try again.

What happens if the iron is too cold?

The insert stops short, or you push hard enough to split the boss. If the insert needs force to go in, the temperature is low rather than the hole being small.

Heat-set insert temperature by material

An insert seats properly when the plastic around it flows and then closes back around the knurls. That happens a little above the temperature the material was printed at, not at soldering temperature.

Material	Typical print temp (°C)	Iron setting (°C)
PLA	195 – 215	≈ 225
PETG	230 – 245	≈ 245
ABS / ASA	240 – 260	≈ 265
Nylon (PA)	250 – 270	≈ 280

Treat these as starting points. Filament brands vary, and a part printed hot for strength wants a hotter iron than the same material printed cool for detail.

Seating the insert flush

A useful technique is to press about ninety percent of the way with heat, lift the iron, and push the last fraction home with a flat cold tool. The plastic sets while the insert is being held square, which leaves the face flush instead of proud or sunken.

Holding an iron vertical by hand while pushing down is the part that fails. A press keeps the tip on one axis and returns it when released.

Common questions

What temperature should I use for heat-set inserts?: The common rule is 10 to 20 °C above the material print temperature: around 225 °C for PLA, 245 °C for PETG, 265 °C for ABS and about 280 °C for nylon.
Which soldering iron should I use?: Any temperature-controlled iron works. What matters is fitting a press tip matched to the insert bore rather than using a normal soldering tip, and keeping the iron vertical, which is what a press does for you.
What happens if the iron is too hot?: The plastic melts too freely, the insert sinks too deep, and a ring of molten material squeezes up around the boss, leaving it weaker. If you see that ring, drop 10 °C and try again.
What happens if the iron is too cold?: The insert stops short, or you push hard enough to split the boss. If the insert needs force to go in, the temperature is low rather than the hole being small.