Eyeglass, watch and hearing aid screws
Below M1.6 the rules change. Tolerances are tighter, the screws are easy to lose, and 'close enough' strips a hinge instantly. Here is what is really in there.
Typical sizes
Glasses hinges are usually around 1.2 to 1.4 mm across the threads, with nose pad screws often the smallest of all. Watch case backs, bracelets and hearing aid housings sit in the same range.
Many optical and watch screws use pitches that do not match standard ISO metric threads, which is why an assortment box screw can feel almost right and still strip the hole.
- Glasses hinge: about 1.4 mm diameter, 2 to 5 mm long
- Nose pad: about 1.2 mm diameter, 1.5 to 2.5 mm long
- Watch bracelet and case back: 1.2 to 1.6 mm typical
- Hearing aid housing: 1.0 to 1.4 mm typical
Measuring something this small
A digital caliper is the only reliable tool here. Zero it, close it gently on the threads, and take the reading twice.
A printed screw gauge card also works: drop the screw through holes until it just passes.
Do not judge by eye. The difference between 1.2 and 1.4 mm is invisible and permanent once you cross-thread the frame.
Tools that actually work
A 1.0 to 1.4 mm flat-blade precision screwdriver covers most glasses. Watch screws often need a 1.2 or 1.4 mm blade with a properly ground tip.
A cheap driver with a rounded tip will chew the slot out in one attempt. Buy one decent driver rather than a 50-piece set of soft ones.
Work over a tray or a towel. These screws vanish on carpet permanently.
Keeping them in
A dab of clear nail polish or a purpose-made screw lock on the threads stops hinge screws walking out, and still lets you undo them later.
Never use strong thread locker on plastic or coated frames — it can craze the plastic and it makes the screw unremovable.
If the hole itself is stripped, a slightly longer screw with a tiny nut behind it, or a hinge repair kit, is safer than jumping up a diameter.
Common questions
Are eyeglass screws a standard size?
Not really. Diameters cluster around 1.2 to 1.4 mm, but pitches and head shapes vary between makers, so the safest route is to measure yours or take the frame to an optician who will fit one free.
Can I use a watch screw in glasses?
Sometimes the diameter matches, but the pitch and head often do not. Test by hand; if it does not spin in freely, do not force it.
What size screwdriver do I need for glasses?
A 1.4 mm flat blade fits most hinges, with a 1.0 or 1.2 mm for nose pads. Some newer frames use a tiny Phillips instead.
The screw keeps loosening. What now?
Clean the threads, add a drop of clear nail polish, and re-tighten firmly but without straining. If the hole is worn out the hinge itself needs repair rather than a bigger screw.
Keep reading
Tools and screws for this job
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Metric screw assortment kit
One box covering the sizes in this guide
Precision driver and bit set
The right bit is what stops rounded heads
Digital caliper
Measure before you buy anything