the same manner as those for plates; for instance, bar 6"
1/16 inch of thickness. Therefore, 5-pound plate is l/8
X 1/2". Bars are available in a variety of cross-sectional
of an inch thick.
shapes, such as round, hexagonal, octagonal, square,
Note in figure 13-16 that 1 cubic foot of steel
and flat. Three different shapes are shown in figure
weighs 490 pounds. This figure divided by 12 is 40.8,
13-18. You may hear both the square and the round bars
which is the weight (in pounds) of a steel plate 1 foot
referred to as RODS or STOCK. Both squares and
square and 1 inch thick. In practice, the .8 is dropped
rounds are commonly used as bracing members for light
and a l-inch steel plate is called 40-pound plate.
structures. Their dimensions, in inches, apply to the
Blueprints will normally list plate using the full decimal
side of the square or the diameter of the round.
designation. The weight of plate, in a number of
different thicknesses, is listed in figure 13-16.
METAL CLASSIFICATION AND
Nonferrous Plate Sizes.--There are numerous
types of nonferrous metals, such as aluminum, brass,
copper, and stainless steel. Each of these metals have
As an HT, you will use different types and alloys of
different weight per square foot. Therefore, nonferrous
different metals on a daily basis. An understanding of
metals are simply measured by their nominal thickness,
the different classification and specification systems
such as l/8, l/4, and l/2 inches.
will greatly aid you in the proper selection and use of
SHEET METAL.--Sheet metal is very similar to
plate metal. Sheet metal is used extensively in the sheet
There are different types of classifications and
metal shop for the manufacture of lockers, bins, shelves,
specifications for different metals used in the Navy.
trim work, false bulkheads, and numerous other
Metal components identified on all blueprints use one
applications. Sheets cut to specific sizes may be
of these classifications or specifications. This section
obtained in widths ranging from a minimum of 6 inches
will discuss the SAE/AISI classification systems,
to 120 inches or more. The thickness of sheets will be
federal, ASTM, and military specification systems and
less than l/8 inch thick and measured by the gauge. The
aluminum classifications used today. We will also look
gauge of sheet metal is determined by a fixed standard
at the continuous metal marking system.
and measured in thousands of an inch, as shown in
figure 13-17. The edges of these plates may be either
SAE/AISI Classification Systems
cut by shears (sheared plates) or rolled square (universal
mill plates). Plates are frequently referred to by their
The Society of Automotive Engineers (SAE) and the
width and thickness in inches, such as plate 24" X 1/2".
American Iron and Steel Institute (AISI) each have
In all cases, the length is given in feet and inches, such
devised systems to identify and classify carbon steels and
steel alloys. These systems are almost identical except
that the AISI adds a letter indicating the process by which
the steel was made. Both systems use a four- or five-digit
The structural shape known as a BAR has a width
of 6 inches or less and is thicker than 3/16 of an inch.
The edges of bars usually are rolled square, just like the
numbering system uses a four-digit numbering system
universal mill plates. The dimensions are expressed in
to identify the type of steel. Infix and suffix letters may
be added to the numbering system. Each number has a
significance as explained in the following paragraphs.
Refer to figure 13-19.
--The first and second digits of the SAE numbering
system indicates the main alloying element and the
approximate percentage of the alloying element in the
steel. Table 13-2 shows the numbers with their
--The third and fourth digits of the SAE number
indicate the percentage of carbon in the steel. Table
13-3 shows the carbon content in hundredths of 1
Figure 13-16.--Weight and thickness of steel plate.