What is a heat-set thread insert?

A heat-set insert is a brass threaded insert that is pressed into a 3D printed part using a soldering iron. The heat melts the surrounding plastic which flows into the knurled outer surface, creating a strong threaded connection. They are far stronger than threading directly into plastic.

What hole size do I need for heat-set inserts?

The hole should be slightly smaller than the insert outer diameter so the insert melts into the plastic. For M3 inserts, a typical hole is 4.5mm. This calculator gives the correct size for each insert type adjusted for your material.

Which material is best for heat-set inserts?

PETG and ABS provide the strongest insert hold due to their higher glass transition temperatures and better flow around the insert knurling. PLA works but is more brittle. All materials benefit from printing the boss with 100% infill or extra perimeters.

What temperature should I use to install inserts?

Use a soldering iron set to the material processing temperature: 200°C for PLA, 230-240°C for ABS, PETG and ASA. Press slowly and straight. A dedicated insert tip for your soldering iron gives the most consistent results.

3DPrintCalcs

Thread Insert Calculator — Heat-Set Insert Sizing for 3D Prints

Calculate hole diameter, depth, wall thickness, installation temperature and pull-out strength for heat-set inserts.

Insert Type

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Number of Inserts

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Material

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How We Calculate This

This calculator provides hole dimensions and installation parameters for standard heat-set brass inserts in 3D printed parts.

How it works

Hole diameter is based on the insert outer diameter with a small clearance. Hole depth is the insert length plus a 0.5mm buffer. Boss diameter ensures sufficient wall thickness around the insert for structural integrity.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.