Greetings Studious CSers, Here is the LM version (less math) of wire gage determination for the non-engineers on the wonderful CS list. The American Wire Gage, also know as the Brown and Sharp Gage, was devised in 1857 by J.R.Brown. It is usually abbreviated AWG. This gage has the property, in common with a number of other gages, that its sizes represent approximately the successive steps in the process of wire drawing. Wire drawing is where a wire is drawn thru a die (metal block with a small hole in it) and in order to make smaller and smaller wire the hole in the dies gets smaller and smaller. Each step is a drawing and may only reduce the size of the wire a small amount, to prevent permanent damage to the material of the wire. After every few drawings the wire must be annealed (softened) before it can be drawn again. The first drawing will give a No.1 wire, three drawings a No.3 wire, thirty drawings a No. 30 wire, etc.. Also, like many other gages, its numbers are retrogressive, a larger number denoting a smaller wire, corresponding to the number of operations of drawing. These gage numbers are not arbitrarily chosen, as in many gages, but follow the mathematical law upon which the gage is founded.
Basis of the AWG is a simple mathematical law. The gage is formed by the specification of two diameters and the law that a given number of intermediate diameters are formed by geometrical progression. (the amount that the wire may be reduced with each drawing) Thus the diameter of No.0000 (4/0) is defined as 0.4600 in. and of No.36 as 0.0050 in. (this is the two end points) There are 38 sizes between these two; hence the ratio of any given diameter to the diameter of the next greater number is given by this expression: 39th root of 0.4600/0.0050 = 39th root of 92 = 1.1229322 (round to 1.123) The square of this ratio = 1.2610 (use 1.26). The sixth power of the ratio, that is, the ratio of any diameter to the diameter of the sixth greater number, = 2.0050 (use 2). The fact that this ratio is so nearly 2 is the basis of numerous useful relations or short cuts in wire computations. There are a number of approxmate rules applicable to the AWG which are useful to remember. 1. An increase of three gage numbers (for example from No.10 to 7) doubles the area and weight and consequently halves the dc resistance. 2. An increase of six gage numbers (for example No.10 to 4)doubles the diameter. 3. An increase of 10 gage numbers (for example No.10 to 1/0) multiplies the area and weight by 10 and divides the resistance by 10 (1/10). 4. A No.10 annealed wire has a diameter of about 0.10 in., an area of about 1,000 mils, and a resistance of approximately 1.0 ohm/1000 ft. (for standard annealed copper at 20deg C.) 5. The weight of No.2 copper wire is very close to 200 lbs/1000 ft. Examples were given in the previous posting. Bless you Bob Lee -- oozing on the muggy shore of the gulf coast [email protected] -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] List maintainer: Mike Devour <[email protected]>
