Jackie Shelton, age 14, of Centralia, Ill., for her question:
HOW IS WIRE MADE?
Copper wire is used for telephones and telegraphs because it is one of the best conductors of electricity. Platinum wire is used in some telescopes because it can be drawn out to great thinness. It has been made as fine as one fifty thousandth of an inch thick. Wire is also used to make nails, fences, watch springs, screens and strings for scientific and musical instruments.
Wire is a flexible metal rod that is drawn out into a long and thin band with a uniform cross section. The only metal that can be used to make wire is one that is ductile, or a metal that can be drawn out.
Wire can be made of copper, iron, brass, aluminum, platinum, gold and silver.
From ancient times until about 1300, wire was made by hammering metal into plates. The plates were then cut into strips and rounded by beating.
In the 1300s the first crude methods of ''drawing'' wire were introduced. Then by the middle of the 1800s in England, a machine was developed that would draw out the metal without the need for hand labor.
Wire making machines use iron or steel billets, which are blocks of metal two inches square. The billets are heated and run through rollers that press them into smaller and longer shapes. They come out as long rods about a quarter of an inch in diameter. The rods are wound on reels while still hot and cleaned in sulfuric acid and water.
Pulling the rods through a number of tungsten carbide dies then draws them out thin to form wire. The die has to have a funnel like shape with a rounded opening that is smaller than the rod.
A rod is pointed at one end and as soon as it goes through the die, it is seized with a pair of pincers and drawn far enough to be attached to an upright drum. The drum rotates and pulls the wire through the die. The wire winds on the drum.
Fine wire may be drawn through a series of dies. Because drawn wire has a tendency to harden, it is softened and made less brittle by being heated in a furnace.
For drawing the finest kinds of wire, extremely hard dies made of diamonds are used.
Wire size differs according to gauge, or diameter. The range varies from gauge No. 000000 which is written as six zeros to No. 51. The No. 000000 denotes a wire that is 0.58 inch in diameter while No. 51 is 0.000878 inch diameter.
Sometimes the Imperial gauge of England is used rather than the standards of the United States. Gauges of Germany and France are in millimeter.