USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 3/TASK 1
the case of steel, large users are thoroughly familiar with the behavior of
existing gages in tooling, especially dies, and do not intend that their
shop personnel be burdened with learning how preferred thicknesses behave.
Another important factor is the sum total of warehouse stock manufactured
with existing gages. You must keep abreast of any change in availability of
metals in these common gaging systems, as opposed to simplified systems.
For example: in the brass industry, the American Standards Association (ASA)
numbers are said to be preferred for simplicity of stocking, but actually
most of the metal is still made to Brown and Sharpe (B&S) gage numbers.
Until single standards are adopted, selecting the right gaging system and
the proper decimal equivalent of the gage numbers is simplified by Table III
on page 208, the index of gaging systems used for various metals and
commodities, and the conversion chart--wire and sheet metal gages in inch
equivalents (figure 158 on page 209). It is good practice to use the inch
equivalent in decimals to at least the third digit, and not a gaging system
number, since the gaging system numbers have different inch equivalents,
depending on the article and metal.
(1) Sheet Metal Gaging Systems.
Several gaging systems are used for
sheet and strip metal.
(a) Manufacturer's Standard Gaging System (Mfr's Std).
This
gaging system is currently used for carbon and alloy sheets. The system is
based on steel weighing 41.82 pounds per square foot (psf), 1 inch thick.
Gage thickness equivalents are based on 0.0014945 in. per oz. psf; 0.023912
in. per lb. psf (reciprocal of 41.82 psf per in. thick); 3.443329 in. per
lb. psf.
(b) U.S. Standard Gaging System (U.S. Std). This gaging system is
obsolete except for stainless steel sheets, cold rolled steel strip (both
carbon and alloy), stainless steel tubing, and nickel alloy sheet and strip.
(c) Birmingham Wire Gaging System (BWG). This gaging system, also
called the Stubs iron wire gaging system, is used for hot rolled steel
carbon and alloy strip and steel tubing.
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