Hinge-making is one of the foundational construction techniques in the jeweller's repertoire, enabling two or more components of a piece to pivot, open, or flex relative to one another. The principle is mechanically simple — interlocking cylindrical sections, called knuckles, are aligned along a common axis and united by a slender pin or wire — yet its execution demands a level of precision that separates competent bench work from fine craftsmanship. Hinges appear throughout the full range of jewellery forms: the barrel clasp of a bangle, the spine of a locket, the articulated body of a brooch, the catch mechanism of a box-set earring. In each case the hinge must move freely, resist wear, and remain invisible or elegantly minimal within the overall design.

Anatomy of a Jewellery Hinge

Every functional hinge consists of three elements: the knuckles, the pin, and the two leaves — the structural surfaces to which the knuckles are attached. The knuckles are short lengths of seamless or drawn tubing, typically fabricated from the same metal alloy as the parent piece to ensure compatible thermal expansion and a consistent visual finish. They are cut to equal lengths so that, when the alternating sections from each leaf are interleaved, the assembled column presents a flush, even profile. The bore — the interior diameter of the tubing — must be sized to accept the pin with minimal play: too loose and the joint wobbles; too tight and it binds or resists movement.

The pin itself is a length of round wire, drawn to match the bore diameter. It may be left as a friction fit, relying on slight compression within the knuckle column to hold it in place, or it may be riveted at one or both ends by lightly peening the protruding wire flush against the outermost knuckle. In high-wear applications — watch cases, heavy bangles, articulated necklace sections — a more secure rivet is preferred. In lighter pieces such as lockets, a friction-fit pin that can be removed for repair is sometimes favoured.

Materials and Tubing Selection

The choice of tubing is consequential. Seamless drawn tubing in gold alloys (yellow, white, or rose gold in 9, 14, or 18 carat), sterling silver, and platinum is standard for fine jewellery. The wall thickness of the tubing must be sufficient to withstand repeated flexion without deforming the bore, yet thin enough that the assembled knuckle column does not appear bulky. A wall thickness of roughly one-fifth to one-quarter of the outer diameter is a widely observed proportion in bench practice, though this varies with the scale of the piece.

For costume or fashion jewellery, brass or nickel-silver tubing is common. Platinum hinges, used in the finest pieces and in watch cases, require particular care during soldering because platinum's high melting point demands hard platinum solder and a focused flame; the surrounding metal must be protected from overheating.

Fabrication Process

The standard fabrication sequence proceeds as follows. First, the tubing is cut into knuckle sections of equal length using a fine-toothed jeweller's saw or a tubing cutter, with each cut made perpendicular to the tube's axis. Any burr on the cut ends is removed by drawing the knuckle lightly across a flat file or abrasive paper, keeping the end face square. The number of knuckles is determined by the length of the hinge and the desired strength: a three-knuckle hinge (two on one leaf, one on the other, or vice versa) is the minimum functional arrangement; five or seven knuckles are used for longer or higher-stress hinges.

The knuckles are then positioned on each leaf in alternating sequence. A length of binding wire or a temporary steel pin — slightly smaller in diameter than the bore — is threaded through the assembled column to hold alignment during soldering. Each knuckle is soldered individually to its respective leaf, using a solder grade appropriate to the sequence of operations: hard solder for the first joints, medium or easy solder for subsequent ones, to prevent earlier joins from re-flowing. Flux is applied carefully to the knuckle-to-leaf interface only; solder must not be allowed to enter the bore, which would seize the pin.

Once all knuckles are soldered and the piece is cleaned and pickled, the temporary alignment wire is removed and the permanent pin is fitted. If the pin is to be riveted, it is inserted so that a small amount of wire protrudes at each end, then peened with a ball-peen hammer or a riveting stake until the end spreads flush. The hinge is then tested for smooth movement and, if necessary, the pin is burnished or the knuckle ends are lightly dressed to eliminate any roughness.

Precision and Common Faults

Misalignment is the most consequential error in hinge-making. If the knuckles on one leaf are not perfectly co-axial with those on the other, the assembled hinge will bind at the point of misalignment, creating uneven wear and, eventually, a fractured knuckle or a bent pin. Alignment is checked before soldering by threading the temporary pin and confirming that it passes through the full column without resistance. Any deviation is corrected at this stage, before heat is applied.

Solder flooding the bore is the second most common fault. It is prevented by using the minimum quantity of solder, applying flux only to the intended join area, and directing the flame away from the bore opening. A bore that has been partially filled with solder can sometimes be cleared by re-heating and drawing the solder out with a fine pick, but in practice a flooded knuckle usually requires replacement.

Unequal knuckle lengths produce a hinge that, when closed, shows a stepped or uneven seam line — a fault immediately visible in finished work. Careful measurement and consistent cutting, ideally using a mitre block or a purpose-made cutting jig, eliminates this problem.

Variations and Specialist Applications

The basic knuckle-and-pin hinge admits several variations suited to specific applications. The box hinge, used in lockets and pill boxes, encloses the knuckle column within a recessed channel so that the hinge is concealed when the piece is closed, presenting a clean exterior line. The piano hinge or continuous hinge runs the full length of a join — seen in long articulated bracelets and some cigarette cases — and is fabricated either as a series of closely spaced knuckles or, in industrial applications, as a single extruded section that is cut to length and soldered in place.

Articulated jewellery — en tremblant brooches, flexible snake bracelets, scale-link necklaces — often employs a simplified hinge principle in which each link carries a single knuckle that interlocks with the next, the pin being replaced by a rivet or a formed wire loop. The cumulative effect of many small articulated joints produces the characteristic fluid movement of these pieces.

In watchmaking, the hinge is refined to tolerances far tighter than those typical in jewellery, with lapped and polished bearing surfaces and precisely fitted pins. The skills overlap, however, and historically the finest jewellery hinges were made by craftsmen trained in both disciplines.

Tools and Reference Literature

The essential tools for hinge-making are a jeweller's saw with fine blades, a mitre block or cutting jig for consistent knuckle lengths, a flat file, binding wire, soldering equipment with appropriate flux and solder grades, a ball-peen hammer, and a riveting stake or flat anvil surface. A pin vice is useful for holding the pin during fitting and riveting.

The most comprehensive English-language treatment of hinge-making in a jewellery context remains Oppi Untracht's Jewelry Concepts and Technology (Doubleday, 1982), which covers knuckle fabrication, alignment techniques, and variant hinge forms in considerable detail. Tim McCreight's The Complete Metalsmith and Anastasia Young's The Workbench Guide to Jewelry Techniques offer accessible introductions to the same subject for the working bench jeweller.