GUIDES / IDENTIFY A HINGE

How to identify a replacement hinge

Hinges carry no part numbers you can look up. What they do carry is geometry — and four measurements pin down almost any model precisely enough for a factory to match it. Here is how we identify hinges from buyer photos every week, written from our side of the bench.

The four measurements

1. Barrel count. Count the knuckles across both halves: 3, 5, or 7. If half the hinge is missing, count what remains — 2 or 3 female barrels implies the total.
2. Charnier width. The width across the barrel stack, in millimeters. This is the spec that decides whether the two halves will interleave at all. Measure with calipers if you have them; a sharp photo against a mm ruler works too.
3. Hole spacing (screw-on types). Center-to-center distance between the mounting holes. Two hinges can look identical and differ here by half a millimeter — which is the difference between a drop-in fit and drilling new holes.
4. Leaf footprint. Width × height of each plate. The replacement's leaf must cover the original's footprint, especially on welded repairs where the old solder pad shows.

How to photograph a hinge for matching

• Top-down and side-on — two angles minimum. The side view reveals barrel height and pin condition.
• Ruler in frame. Lay the part next to a millimeter ruler in the same focal plane. A coin works as a fallback scale.
• Both halves — frame side and temple side, even if only one is broken. Pairs are matched as pairs.
• Any markings. Logos or digits stamped on the leaf shortcut the search. Photograph them even if half-worn.
• Sharpness beats resolution. A steady phone photo in daylight outperforms a blurry close-up. Tap to focus on the barrels.

Common failure modes (and what they mean for the order)

Ovalized barrels — the temple wobbles even with a tight screw. The hinge is worn out; replace the pair. Stripped pin thread — the screw no longer bites; sometimes an oversize screw saves it, usually the female barrel is gone. Pulled rivets — the hinge tore out of the acetate; the replacement needs the same pin pattern, or a screw-on conversion plate that covers the damage.

When there is no exact match

Discontinued models are our daily business. If the exact hinge no longer exists anywhere, the practical routes are: the nearest standard fit (same barrels and spacing, cosmetic differences), a cover plate that bridges old holes or scars, or — for volume — a small custom run on existing tooling. Send photos through the photo matching service and we tell you which route applies before you spend anything.

Frequently asked questions

How do I measure an eyeglass hinge for replacement?

Four numbers identify most hinges: barrel count, charnier width (across the female barrels), hole spacing center-to-center (for screw-on types), and leaf footprint (width × height). Measure in millimeters with calipers or a ruler photographed beside the part.

Can a broken eyeglass hinge be replaced?

Usually yes. Screw-on hinges swap with a screwdriver; welded hinges need re-soldering by a repair lab; rivet-on hinges are re-staked. The hard part is sourcing a matching hinge — which is a photo-matching problem, not a repair problem.

What if my exact hinge is discontinued?

A factory with a deep model library can usually supply the nearest fit — same barrel count and hole spacing, minor cosmetic differences — or adapt with a slightly different leaf that covers the original footprint.