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Steelworker Volume 02 - Building manual for how to work with steel | Next
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CHAPTER 2
LAYOUT AND FABRICATION OF SHEET-METAL AND
FIBER-GLASS DUCT
As a Steelworker you are required to operate
sheet-metal tools and to apply basic sheet-metal layout
techniques. In many Naval Construction Force (NCF)
projects, sheet metal is used to protect the exterior of
buildings by using flashing, gutters, and at times,
complete sheet-metal roofing systems. Other items
made from sheet metal are dust collection systems,
machinery guards, lockers, and shelving.
Although many of the parts and fittings used in
sheet-metal work are stock items, which are simply
installed or assembled, Steelworkers are required to
fabricate parts and fittings frequently in the shop or to
modify them to fit irregularities in the project design.
Therefore, you must have knowledge not only in
laying out patterns but also have the skills required to
cut, bend, shape, assemble, and install the finished
sheet-metal products. This chapter describes some of
the methods of measuring, marking, cutting, forming,
and joining as well as installing sheet-metal sections,
duct systems, and fiber-glass ducts. In addition, the
use of various hand tools and power tools required in
sheet-metal layout and fabrication is provided.
SHEET-METAL LAYOUT AND CUTTING
TOOLS AND EQUIPMENT
Numerous types of layout tools, cutting tools, and
forming equipment are used when working with sheet
metal. This section will describe the uses of the layout
and cutting tools and the operation of the forming
equipment.
LAYOUT TOOLS
The LAYOUT of metal is the procedure of
measuring and marking material for cutting, drilling,
or welding. Accuracy is essential in layout work.
Using erroneous measurements results in a part being
fabricated that does not fit the overall job. This is a
waste of both time and material. In most cases, you
should use shop drawings, sketches, and blueprints to
obtain the measurements required to fabricate the job
being laid out. Your ability to read and work from
blueprints and sketches is paramount in layout work.
If you require information on blueprints, you will find
chapters 1-3 and 8 of Blueprint Reading and
Sketching, NAVEDTRA 10077-F1, an excellent
reference.
Layout tools are used for laying out fabrication
jobs on metal. Some of the more common layout tools
that you will use in performing layout duties are as
follows: scriber, flat steel square, combination square,
protractor, prick punch, dividers, trammel points, and
circumference rule.
Scriber
Lines are scribed on sheet metal with a SCRATCH
AWL, coupled with a STEEL SCALE or a
STRAIGHTEDGE. To obtain the best results in
scribing, hold the scale or straightedge firmly in place,
and set the point of the scriber as close to the edge of
the scale as possible by tilting the scriber outward.
Then exert pressure on the point and draw the line,
tilting the tool slightly in the direction of movement
(fig. 2-1). For short lines, use the steel scale as a guide.
For longer lines, use a circumference rule or a
straightedge. When you have to draw a line between
two points, prick punch each point. Start from one
prick punch mark and scribe toward the center.
Figure 2-1—Scribing a line.
2-1
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