Locket Pendants: Hinge, Size and What Fits Inside
A locket is the one piece of jewellery that is also a container, and everything about it follows from that. The hinge sets its lifespan, the interior depth sets what fits, and the seam sets what it will survive.
The hinge decides the life
Almost every locket failure is a hinge failure, and the type of hinge predicts when. A barrel hinge runs a steel pin through three to five interlocking knuckles, usually 0.5 to 0.8 mm across; the pin works in shear and is retained by a small head or by friction alone. Well made, it tolerates several thousand open-and-close cycles. When it fails, the pin walks out sideways and the two halves separate — repairable, but only by someone who can remake a pin to match.
The alternative is a living hinge: a thin section of the same metal, folded and bent instead of pinned. It is cheaper to make and impossible to repair, because the metal at the fold work-hardens and cracks after a few hundred to a couple of thousand cycles. If you open a locket daily, this is the detail to ask about.
Sizes and inner capacity
Nominal size is the outside diameter. Usable space is smaller, because the rim, the hinge knuckles and the door thickness all take up room. As a rule the inner frame accepts a photograph about two-thirds of the outside diameter.
| Outside diameter | Photo that fits | Interior depth | Typical use |
| 12 mm | 8 mm | 1.2 mm | Single photo, hair only |
| 15 mm | 10 mm | 1.5 mm | Smallest readable face |
| 20 mm | 13 mm | 2.5 mm | Two photos, back to back |
| 25 mm | 17 mm | 3 mm | Photo plus a lock of hair |
| 30 mm | 22 mm | 3.5 mm | Two portraits, engraved reverse |
Photographs, cut to size
Print at 300 dpi and cut to the inner frame, not to the outer diameter — a 20 mm locket takes a 13 mm print with no margin. Photo paper is 0.1 to 0.2 mm thick, so two portraits sitting back to back need about 1.5 mm of clearance on each side to close without pressure on the hinge. Glossy paper behind glass fogs in humid weather; a matte print or a laser print on thin card stays legible for years.
Hair, paper and what migrates
A lock of hair should be 2 to 3 mm thick, tied at one end with cotton thread and laid flat rather than coiled, or it lifts the door. Loose, untied hair migrates: the seam between the halves is a gap of 0.05 to 0.1 mm, and over months fine strands work through it. Paper is the more forgiving filling, but it holds moisture, and a folded note left against unpolished silver will mark it where it touches.
Weight and how it hangs
An empty 20 mm silver locket shell weighs 4 to 7 g; loaded with two prints and a glass, 6 to 9 g. That mass hangs off a bail whose axis sits proud of the locket face by the thickness of the door, so the piece leans forward on a thin chain. Below 1.2 mm the chain cannot hold the axis, the locket tips and the door edge wears a bright spot against whatever it rests on. A 25 mm locket or larger wants 1.5 mm chain, and a bail wide enough that the locket cannot slide along it.
What "sealed" actually means
There is no gasket. A locket closes on metal against metal, and the hinge is an open bearing; neither is watertight. Steam is worse than water, because it expands the air inside, and when the piece cools the contraction pulls moisture in through the seam along with whatever soap or perfume was on the surface. Chlorine attacks the hinge pin. Take it off before a shower, a bath or a swim, and expect the inside faces to tarnish faster than anything you can reach with a cloth — that is the reason to open it and wipe the interior twice a year.
Opening it without damage
Use a thumbnail in the seam at the point opposite the hinge, and press rather than lever. A blade concentrates force on one spot of a 0.6 mm rim and lifts the edge out of true, and a rim that is out of true will never close flush again. If the door resists, the pin is binding rather than the catch being stiff: a drop of light oil on the knuckles and a few gentle cycles will free it, where force will bend the door.
What we make
We make locket pendants in our own factory in Guangxi, which we have operated since 2008, in 925 sterling silver, 9K, 14K and 18K gold and PT950 platinum, with barrel hinges rather than folded ones. Sizing is quoted as outside diameter and interior depth in millimetres, because the second number is what decides whether a photograph fits. Stones, where used, are GRA-certified D-colour VVS1 moissanite or IGI-certified lab-grown diamonds. Prices run from $17 to $2,020, with a typical piece around $98.
Free shipping over $99, $5.99 below. Returns accepted for 30 days on unworn pieces in original packaging; engraved lockets are made to order and cannot be returned. Interior depth and photo size are stated on every piece so the print can be cut before the locket arrives.