gauge

(ga)

   1. a traditional unit measuring the interior diameter of a shotgun barrel. The gauge of a shotgun was the number of lead balls, each of a size just fitting inside the barrel, that were required to make up a pound. In other words, if a lead ball weighing 1/12 pound just fit in the barrel of a shotgun, then it was a 12-gauge shotgun. Today, the internal diameters for each gauge number are read from a table.

   2. a unit expressing the fineness of a knitted fabric, equal to the number of loops per 1.5 inches (38.1 millimeters).

   The same unit is also used to express the size of the knitting needles used to create a fabric of that fineness.

   3. a traditional unit measuring the diameter (or the cross-sectional area) of a wire. Various wire gauge scales have been used in the U.S. and Britain. In traditional scales, larger gauge numbers represent thinner wires. (For very thick wires, repeated zeros are used instead of negative numbers, so gauges 00, 000, and 0000 represent -1, -2, and -3, respectively.) In the American Wire Gauge (AWG) scale, 0000 gauge represents a wire having a diameter of 0.46 inch and 36 gauge represents a diameter of 0.005 inch (5 mils). Diameters for the other gauges are obtained by geometric interpolation, meaning that the ratio between successive diameters is a constant, except for necessary roundoff. Thus n gauge wire has a diameter of .005·92^((36-n)/39) inch. The metric wire gauge number is equal to 10 times the diameter of the wire, in millimeters; thus a metric 8 gauge wire has diameter 0.8 millimeters. A table of wire gauge equivalents is provided.

   4. a traditional unit measuring the thickness of sheet metal. Larger gauge numbers represent thinner metal: 10 gauge represents a thickness of 0.1345 inch (3.416 millimeters) and each increase of 1 in the gauge number corresponds to a reduction of about 10% in the thickness. A table is provided.

   5. a traditional unit measuring the thickness of plastic film. For this purpose 1 gauge equals 0.01 mil¹ or 10^-5 inch (0.254 micrometer).

   6. a traditional unit measuring the thickness of tennis racquet strings. There are two systems in use. In the U.S. system larger gauge numbers indicate thinner strings; in the European system larger gauge numbers indicate thicker strings. A table is provided.