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RE: gauge of material

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>btw: does anyone know the origins of gage #s?  
The original gauge numbers (iron sheets) were based on weight-- 3 gage 
started out as the thickness of a wrought iron wrought iron (assumed 480 
lb/ft3) plate weighing 10 lb/ft2. I have an 1954 vintage screw thread 
selector that shows approximate weights per square foot of steel sheet as 
follows:

Gage	wt/ft
3	10
4	9.375
5	8.75
6	8.125
7	7.5
8	6.875
9	6.25
10	5.625
11	5
12	4.375
13	3.75
14	3.125
15	2.875
16	2.5
17	2.25
18	2
19	1.75
20	1.5
21	1.375
22	1.25
23	1.125
24	1
25	0.875
26	0.75
27	0.6875
28	0.625
29	0.5625
30	0.5
31	0.4375

These are fairly accurate for a steel density of 501 lb/ft3 (It's 
actually about 490 lb/ft2). My guess is that the gage tables were set up 
with a nice orderly scheme but things got screwed up a little. 
Machinery's Handbook (yeah, I know--obscure nonsense used by ME's wearing 
green eyeshades and garters ;-> ) has a pretty good rundown on all the 
archaic beginnings of this stuff.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
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