Birmingham wire gauge

The steps are irregular. Departmental sanction by the United States government ended in 1914.

Birmingham Wire Gauge
Gauge Diameter,
Area of cross-section,
square centimeters
Resistance,
copper,
ohms per meter
Weight,
copper,
grams per meter
inches centimeters
00000 0.500        
0000 0.454 1.153      
000 0.425 1.079      
00 0.380 0.965      
0 0.340 0.864      
1 0.300 0.762      
2 0.284 0.721      
3 0.259 0.658      
4 0.2320 0.589      
5 0.2120 0.538      
6 0.1920 0.488      
7 0.1760 0.447      
8 0.1600 0.406      
9 0.1440 0.366      
10 0.1280 0.325      
11 0.1160 0.295      
12 0.1040 0.264      
13 0.0920 0.234      
14 0.0800 0.203      
15 0.0720 0.183      
16 0.0640 0.163      
17 0.0560 0.142      
18 0.0480 0.122      
19 0.0400 0.102      
20 0.0360 0.0914      
21 0.0320 0.0813      
22 0.0280 0.0711      
23 0.0240 0.0610      
24 0.0220 0.0559      
25 0.0200 0.0508      
26 0.0180 0.0457      
27 0.0164 0.0417      
28 0.0149 0.0376      
29 0.0136 0.0345      
30 0.0124 0.0315      
31 0.0116 0.0295      
32 0.0108 0.0274      
33 0.0100 0.0254      
34 0.0092 0.0234      
35 0.0084 0.0213      
36 0.0076 0.0193      

sources

1

This is abbreviated B. W. G. It is the same as Stubs' Iron Wire Gauge, but entirely different from Stubs' Steel Wire Gauge. Galvanized Telegraph and Telephone Wire, both bare and insulated, and Galvanized Armor Wire are usually designated by this gauge. Its use is not very extensive and is becoming less.

Wire in Electrical Construction.
Trenton, NJ: John A. Roebling's Sons Company, 1916.
Page 51.

2

This gauge (hereinafter referred to as the B. W. G.) is represented by a series of numbered slots or cuts on the edges of a small rectangular steel plate. It is the practice to distinguish the diameters of wires and the thickness of plates of metal by the number of the slot or cut which the wire or plate may fit.

There is no standard of such gauge or common agreement amongst those interested as to what are the dimensions in parts of an inch of the several slots or sizes of the true B. W. G. Its sizes are not geometrically or arithmetically progressive, and, consequently, bear no definite relation to each other. Its origin is obscure, and it would appear that the several slots or sizes arose from time to time as a new wire or new plate was introduced, and as the exigencies of a particular trade demanded. Considerable annoyance to engineers and pecuniary loss to contractors is stated to occur from a want of accuracy in the copies of this gauge, and the necessity of establishing a standard has lately been discussed, both in this country and in the United States.

Board of Trade.
12th Annual Report to Parliament on Standard Weights and Measures, for 1877-78.

for further reading

Thomas Hughes.
The English Wire Gauge, with Descriptive Tables and Drawings.
London: Spon & Co., October, 1879.

[Committee].
Report to the Council of the Society of Telegraph Engineers on the Birmingham Wire Gauge.
Journal of the Society of Telegraph Engineers
, vol 8, pages 476-504, 1879.

A full discussion of the situation. In at least some copies, bound at the end of the volume is a second copy of the report, followed by “On the Unit of the Birmingham Wire Gauge”, by C.V. Walker, a discussion of that paper, and finally Latimer Clark's 1867 paper, “On the Birmingham Wire Gauge”.

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