Heat-Set Insert Size Chart
Typical dimensions for standard knurled brass heat-set inserts — check your specific insert's datasheet for exact figures, since brands vary slightly.
| Insert | Hole diameter | Min. boss O.D. | Typical length | Install temp |
|---|---|---|---|---|
| M2 | 3.0–3.2mm | 5mm | 3–4mm | ~230–250°C |
| M2.5 | 3.5mm | 5.5mm | 4mm | ~230–250°C |
| M3 | 4.0–4.2mm | 6mm | 4–6mm | ~250–280°C |
| M4 | 5.6mm | 7.5mm | 6–8mm | ~250–280°C |
| M5 | 6.4–6.7mm | 8.5mm | 8mm | ~250–280°C |
| M6 | 8.1mm | 10mm | 8–10mm | ~250–280°C |
Hole diameter matters more than it seems
Too tight and the insert won't seat straight, cracking the surrounding plastic as it's forced in; too loose and it goes in with no resistance and can spin freely in the hole under torque, which defeats the point of using one at all. Print a quick test hole at the listed size in scrap material before committing to a full part if you haven't used that exact insert brand before — the small variations between manufacturers are enough to matter here.
Installing without a dedicated soldering iron tip
A regular soldering iron works fine without a specific insert tip — heat the iron to the temperature above, lower the insert into the hole squarely (a set of tweezers or needle-nose pliers helps keep it straight), and let the iron's heat alone melt it down flush, then remove the iron and let it cool undisturbed for a few seconds before handling. Going in at an angle is the most common mistake and is very hard to correct once the insert is partway in.
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