Table 12-1.--Gauge and Decimal Measurement of Uncoated
the blades all the way, the finished cut will tend to be
Low-Carbon Steel and Zinc-Coated Low-Carbon Steel
Figure 12-57 shows combination snips being used
to cut an outside circle. The metal will be easier to
handle during cutting if you cut away the excess metals
on the corners first. When cutting out the circle, make
a continuous cut, turning the metal as you cut.
Figure 12-58 shows the procedure for cutting out
an inside circle with aviation snips. To start the cut,
Figure 12-56.--Bench shears.
FABRICATING SHEET METAL
The various sheet metal alloys most commonly
used aboard ship include zinc-coated low-carbon steel
(often called galvanized iron), uncoated low-carbon
steel, aluminum, Monel, copper-nickel alloy, copper,
Sheet metal will be identified by either a gauge
number or by a decimal measurement. Table 12-1 shows
the relationship between the gauge and decimal
thickness for uncoated low-carbon steel and for
zinc-coated low-carbon steel. Tables arc available for
other materials. The gauge number of sheet metal is
often stenciled on the metal. If by chance the gauge
number does not appear on the sheet, you can find it by
Figure 12-57.--Cutting an outside circle with combination snips.
measuring the thickness of the material with a U.S.
standard gauge for sheet and plate iron and steel. Then
use table 12-1 to convert the measured thickness to its
CUTTING SHEET METAL
Several types of snips and shears are used to cut
sheet metal. Snips are used to cut the lighter gauges of
sheet metal. Bench shears, such as the type shown in
figure 12-56, are used to cut heavier sheet metal.
Before using either the snips or the shears to cut
sheet metal, make sure you have the right tool for the
Keep the blades at right angles to the work while
you make the cut. The blades should be almost closed,
Figure 12-58.--Cutting an inside circle with aviation snips.
but not quite, to their full length on each cut. If you close