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American standard for copper wire
||The American Standard gage
is used to measure copper wire. It is a disc with various sizes of
holes cut around its edge. The holes are calibrated for wires from
No. 0000 to No. 36; No. 0000 corresponds to .3065 of an inch, and
No. 36 corresponds to .0090 of an inch. These numbers correspond to
those of the Brown and Sharpe gage for copper wire.
Birmingham and the stubbs gages for iron
The English standard gage is the Birmingham
or Stubbs gage. It is also used widely in the United States. The Birmingham
gage resembles the American Standard Wire Gage. It is generally used for
the measurement of iron wire, although it is sometimes used as a sheet-copper
gage. The numbers on this gage range from 6 to 36.
Use of wire gages
To gage a wire, insert it in one hole of
the proper gage after another until you find the hole it just fits in.
The number of that hole gives you the gage number of the wire.
Efforts are now being made to reduce the
number of standards used in wire gages. In the meantime, many engineers
in designing machinery ignore the gage numbers and specify all wire diameters
in decimals of an inch.
To meet the condition, circular gages are
made with the number or letter size marked on one side of the gage and
the decimal equivalent marked on the other. A further complication enters
when parts must be matched with dimensions given in the metric system.
This requires calculation of each dimension or the use of the metric conversion
Figure shows a gage with a V-opening. This
type of gage may be obtained calibrated in gage numbers, decimals, and
various combinations of units. In use, the wire, screw, or rod being measured
is allowed to rest lightly in the groove and the gage marking at the point
of contact indicates its size. In using any of these gages, it is obvious
that the accuracy of the reading is dependent upon how closely the part
measured fits the gage.
Of course, if the part
measured is forced in, the reading has no meaning and the gage itself
may be damaged. On the other hand, if the fit is too loose, the
reading on the gage will not indicate the true measurement. With
practice, a delicate sense of touch is developed which tells the
user of a gage When the fit is correct. Ability to measure accurately
and quickly will increase as the beginner develops this touch.
Manufacturers take great pains to
make gages accurately. The surf aces of the gages are hardened to
preserve this accuracy. In use, they must be protected from acid
fumes and from moisture. After using they should be wiped with an
oily cloth and returned to a protective container. Like other measuring
tools, they should never be used for any purpose other than measuring.
If a gage is accidentally damaged in a way
to affect its accuracy, it should be destroyed or, if the cost justifies
it, it may be returned to the manufacturer for recalibration. If it is
left available, its use while damaged may lead to errors, costly in waste
of material and time.
Sheet metal gage
||A circular gage, similar
to the wire gage shown, is used for sheet and plate iron and steel.
It is illustrated. It is used in exactly the same manner as the circular
wire gage, and differs from it only in the relation of the gage openings
to the gage numbers.