Half-round wire — also known as D-wire or D-section wire — is a jewellery-making stock whose cross-section describes a precise semicircle: one face is flat, the other convex and rounded. This deceptively simple geometry makes it one of the most practically useful wire profiles in the bench jeweller's repertoire, combining a stable, solderable flat face with a smooth, comfortable or decorative outer surface. It is produced in gold, silver, platinum, palladium, and a range of base and filled metals, and is supplied in widths typically spanning 0.5 mm to 6.0 mm.

Manufacture and Profile

Half-round wire begins as round wire or rod stock and is progressively drawn through a series of shaped dies — each die presenting a D-shaped aperture — until the desired cross-sectional dimensions are achieved. The drawing process work-hardens the metal, so intermediate annealing is required for softer, more ductile alloys such as fine silver or high-carat gold. The finished wire is supplied in coils or straight lengths and is classified by the width of its flat face, which corresponds to the overall diameter of the equivalent round wire from which it is derived. Because roughly half the circular cross-section is removed in forming the D-profile, the wire carries significantly less metal mass per linear metre than round wire of the same nominal height — a meaningful consideration when working in platinum or high-carat gold, where material cost is substantial.

Applications at the Bench

The dual geometry of half-round wire suits it to several distinct bench applications:

• Bezel setting. The flat inner face sits flush against the base plate or gallery, providing maximum contact area for soldering and a clean interior wall against which a stone's girdle will seat. The rounded outer face presents a finished, polished profile without further shaping.
• Ring shanks. A shank formed from half-round wire — flat face inward — conforms comfortably to the finger, reducing the sharp edges that can occur with square or rectangular section wire, while the rounded exterior requires minimal filing or finishing.
• Decorative borders and gallery strips. When applied around the perimeter of a brooch, locket, or box lid, half-round wire creates a neat raised border that reads as a moulding, echoing architectural detail at a miniature scale. It is a standard element in Victorian and Edwardian work, and continues in contemporary production.
• Collet construction. Simple collets for cabochon or faceted stones are readily formed by bending half-round wire into a ring, soldering the join, and sizing to the stone's girdle diameter — the flat face providing an automatic seating ledge.

Metal Varieties and Gauges

Half-round wire is a standard catalogue item from bullion dealers and findings suppliers in sterling silver (925), fine silver (999), yellow, white, and rose gold alloys from 9 ct through 22 ct, platinum (950 and 900), and palladium. Copper, brass, and argentium silver versions are widely available for students and production work. Gauge systems vary by region: British suppliers typically specify width in millimetres; American suppliers may additionally reference the Brown & Sharpe (B&S) or American Wire Gauge (AWG) system, though these are more naturally suited to round wire and require conversion for D-section stock. The most commonly stocked widths in precious metal are 1.0, 1.5, 2.0, 3.0, and 4.0 mm, with finer and heavier gauges available to order.

Working Characteristics

Because the drawing process introduces work-hardening, half-round wire purchased in coil form is generally supplied in a half-hard or hard temper. Annealing to a dead-soft state before forming is advisable when tight curves or complex bends are required, particularly in platinum, which work-hardens rapidly and demands careful heat management. Silver and gold alloys respond readily to standard annealing protocols. The flat face should be kept clean and free of firescale before soldering; a light pass with fine emery paper along the flat is common practice to ensure intimate contact with the base metal and a sound solder join.