standard wire gauge

SWG was fixed by Order of Council August 23, 1883. It was constructed by improving the Birmingham Wire Gauge. It was made a legal standard on 1 March, 1884, by the British Board of Trade. SWG is not to be confused with American wire gauge, which has a similar but not interchangeable numbering scheme.

A table of the gauge numbers and wire diameters is shown below.LewcoS Wire Tables 1962{{cite web |last1=Rowlett |first1=Russ |author2=University of North Carolina at Chapel Hill |author2-link=University of North Carolina at Chapel Hill |title=American and British Wire Gauges |work=How Many? A Dictionary of Units of Measurement |url=https://www.unc.edu/~rowlett/units/scales/wiregauge.html |publisher=University of North Carolina at Chapel Hill |access-date=2011-04-06 |archive-url=https://web.archive.org/web/20180802083925/https://www.unc.edu/~rowlett/units/scales/wiregauge.html |archive-date=2018-08-02 |date=2001-03-02}} The basis of the system is the thou (or mil in US English), or {{nowrap|0.001 in}}. Sizes are specified as wire diameters, stated in thou and tenths of a thou (mils and tenths). The wire diameter diminishes with increasing size number. No. 7/0, the largest size, is {{nowrap|0.50 in.}} (500 thou or {{nowrap|12.7 mm}}) dia., No. 1 is {{nowrap|0.30 in.}} ({{nowrap|300 thou}}), and the smallest, No. 50, is {{nowrap|0.001 in.}} ({{nowrap|1 thou}} or {{nowrap|25.4 µm}}).

The system as a whole approximates an exponential curve, plotting diameter against gauge-number (each size is a approximately a constant multiple of the previous size). The weight per unit length diminishes by an average of approximately 20% at each step. Because the weight per unit length is related to the cross sectional area, and therefore to the square of the diameter, the diameter diminishes by approximately 10.6%:

:$\backslash mbox\{Diameter\; Ratio\}\; =\; 1-\backslash sqrt\{1-0.2\}\; \backslash approx\; 10.6\backslash \%$

However, the system is piecewise linear, only approximating the exponential curve loosely. Thus, it runs in constant steps of {{nowrap|0.4 thou}} ({{nowrap|0.4 mil}}) through the range No. 49 - No. 39 and of {{nowrap|0.8 thou}} ({{nowrap|0.8 mil}}) through No. 39 - No. 30.

• IEC 60228, the metric wire-size standard used in most parts of the world.
• Circular mil, Electrical industry standard for wires larger than 4/0.
• American Wire Gauge (AWG), used primarily in the US and Canada
• Stubs Iron Wire Gauge
• Jewelry wire gauge
• Body jewelry sizes
• Electrical wiring
• Number 8 wire, a term used in the New Zealand vernacular

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Category:Wire gauges

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