Stripped thread repair sizer
The screw spins forever and never tightens. That is the hole, not the screw. Pick what the hole is made of and get the fix with real drill sizes.
Best fix
Fit a brass heat-set insert
- Open the boss to about 4.0 mm for an insert with roughly a 4.6 mm outside diameter.
- Push the insert in with a soldering iron at 200–250 °C, straight and slow, until it sits flush.
- The hole then takes a normal M3 machine screw and survives repeated opening.
- No insert to hand? A short-term fix is a plastic wall plug sliver or a cocktail stick and glue, then re-drive the original self-tapping screw.
All sizes at a glance
| Size | Next size up | Coil drill / tap | Heat-set hole |
|---|---|---|---|
| M1.6 | M2 | — | 2.6 mm |
| M2 | M2.5 | 2.1 mm / M2.2 | 3.2 mm |
| M2.5 | M3 | 2.6 mm / M2.7 | 3.6 mm |
| M3 | M3.5 or M4 | 3.2 mm / M3.2 | 4.0 mm |
| M4 | M5 | 4.2 mm / M4.2 | 5.6 mm |
| M5 | M6 | 5.2 mm / M5.2 | 6.4 mm |
| M6 | M8 | 6.3 mm / M6.3 | 8.0 mm |
Insert dimensions vary by brand — check the packet before drilling, because you cannot put metal back.
What you need for this repair
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Thread repair / helicoil kit
Coil inserts, drill and tap in one box
Heat-set brass inserts
The fix for plastic and 3D-printed holes
Next-size-up screw kit
Sometimes going one size up is the whole repair
Keep going
Repair kit builder
Build a screw assortment for laptops, phones, drones or 3D printers and see exactly what to buy.
Screw size finder
Type in what you measured with a caliper and get the metric size, pitch and likely length.
Tap & clearance hole calculator
The exact drill size to tap M1.2 to M6, plus close and normal clearance holes.
Metric ↔ imperial converter
Convert mm to inches, and see which US screw number sits closest to each metric size.