Plainwire / Reference / Screw heads and drivers
Screw heads and drivers
A lookup table, so that guides can say “Torx T6” and link here rather than explaining it again. Sizes given are what we have actually met in domestic equipment, not the full standard.
Heads you will meet
| Head | Common sizes | Where it turns up | Notes |
|---|---|---|---|
| Phillips (PH) | PH0, PH1, PH2 | Everything with a metal chassis | Designed to cam out under torque. That is a feature on an assembly line and a nuisance on a seized screw. |
| JIS | J0, J1, J2 | Japanese-designed equipment, older cameras and audio | Looks like Phillips, is not. A Phillips driver in a JIS screw rounds it. Identified by a small dot stamped beside the cross. |
| Pozidriv (PZ) | PZ1, PZ2 | European appliance chassis, mains terminals | Four extra ticks between the cross arms. Does not cam out, which is why it is used where torque matters. |
| Torx (T) | T5 to T20 | Laptops, kettles, power tools | The default modern fastener. T6 and T8 cover most consumer electronics. |
| Torx Plus | IP5 to IP15 | Higher-torque assemblies | Slightly squarer lobes. A Torx bit fits loosely and will round it. |
| Torx security | T6H to T20H | Anything a manufacturer would rather you left alone | Same as Torx with a post in the centre. Needs a bored bit. |
| Tri-point (Y) | Y000, Y00, Y0 | Phones, games controllers, some kettles | Three lobes. Very easy to strip; go slowly and press hard. |
| Tri-wing | 1, 2, 3 | Games consoles, older handhelds | Three vanes offset from centre, unlike tri-point. |
| Pentalobe (P) | P2, P5, P6 | Phone and laptop outer cases | Five rounded lobes. The bits are cheap now; do not improvise. |
| Hex / Allen | 1.3 to 4 mm | Lamp arms, hinges, anything with a clamp | Metric and imperial are close enough to fool you and different enough to round. |
| Spanner (snake eye) | 4, 6, 8 | Public-facing fittings, some cabinets | Two round holes. Rarely inside consumer goods. |
Choosing a driver
Fit matters more than brand. A bit that rocks in the recess is the wrong bit, and using it once will make the correct bit not work either. Three practical rules:
- Press before you turn. Something in the order of seventy per cent of your effort should be axial. Stripped heads are almost always a pressure failure rather than a torque one.
- Turn slowly at the start. If the screw does not move on the first quarter turn, stop and reassess — another quarter turn will round it.
- Use the longest driver that fits. Length gives you the axial alignment that stops the bit from tilting.
Getting a rounded screw out
| Method | When it works |
|---|---|
| A wide band of rubber (a cut glove finger) between bit and screw | Lightly rounded, not seized. Fills the recess and grips. |
| A flat-blade driver ground to fit the wreckage | Larger screws where there is metal left to bite. |
| Screw extractor, left-hand spiral | Steel screws in steel. Poor on the soft alloy screws used in electronics. |
| Cut a slot with a rotary tool | The head is proud and there is nothing fragile within a centimetre. Produces conductive swarf; mask everything first. |
| Drill the head off | Last resort. The shank usually then turns out with pliers once the clamped part is free. |
Thread-locker
Blue residue in the threads is a medium-strength anaerobic locker. It softens at around 130 °C, which a soldering iron pressed against the screw head for twenty seconds will reach without harming a plastic housing nearby. Red is high-strength and is not coming out without heat you should not apply to a domestic appliance.
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