A wire is a flexible, round bar of metal. Wires are commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in various standard sizes, as expressed in terms of a gauge number or cross-sectional area. Wires are used to bear mechanical loads , often in the form of wire rope. In electricity and telecommunications signals , wire can refer to electrical cable , which can contain a solid core of a single wire or separate strands in stranded or braided forms.
Usually cylindrical in geometry, wire can also be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound coil springs , such as the Slinky toy, are made of special flattened wire. In antiquity , jewelry often contained large amounts of wire in the form of chains and applied decoration that was accurately made and which must have been produced by some efficient, if not technically advanced, means.
In some cases, strips cut from metal sheet were made into wire by pulling them through perforations in stone beads. This causes the strips to fold round on themselves to form thin tubes. This strip drawing technique was in use in Egypt by the 2nd Dynasty c. From the middle of the 2nd millennium BCE most of the gold wires in jewelry are characterized by seam lines that follow a spiral path along the wire. Such twisted strips can be converted into solid round wires by rolling them between flat surfaces or the strip wire drawing method.
The strip twist wire manufacturing method was superseded by drawing in the ancient Old World sometime between about the 8th and 10th centuries AD. Square and hexagonal wires were possibly made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between a grooved punch and a grooved metal anvil.
Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BCE in Egypt and in the Bronze and Iron Ages in Europe for torcs and fibulae. Twisted square-section wires are a very common filigree decoration in early Etruscan jewelry. In about the middle of the 2nd millennium BCE, a new category of decorative tube was introduced which imitated a line of granules. True beaded wire, produced by mechanically distorting a round-section wire, appeared in the Eastern Mediterranean and Italy in the seventh century BCE, perhaps disseminated by the Phoenicians.
