SHEET METAL LAYOUT AND FABRICATION
Upon completion of this chapter; you will be able to do the following:
Define some of the basic terms used in the layout and fabrication of sheet
Describe the basic techniques used to perform various sheet metal layout
operations and define the three types of plans
Recognize the various methods of pattern development
Describe some of the tools and equipment generally found in the sheet metal
shop, and describe their use and operation
Describe the safety procedures and equipment used in sheet metal fabrication
A BLUEPRINT is a duplicate of a drawing or
sketch. Usually, only accurate drawings are blueprinted.
As a Hull Maintenance Technician (HT), you may
These blueprints are furnished by the manufacturers of
be assigned to lay out and fabricate ventilation ducts,
the machinery installed aboard your ship and also by the
drip pans, and other items made from sheet metal. In
command concerned with the building and maintenance
this chapter, we will look at the tools and methods that
of the ship on which you are serving.
you will use for jobs of this sort. We will also look at
If you have not done so, this is a good time to study
pattern development, the transfer of a pattern to sheet
Blueprint Reading and Sketching, NAVPERS 12077-E
metal, and the fabrication of the sheet metal projects.
You must be able to read plans accurately, and this book
NOTE: You will not be able to do the layouts in this
will help you to read almost any type of plan. A
chapter unless you learn each step of each process as
satisfactorily completed job is your objective, and the
plans are essential guidelines. As you study this chapter,
you go along. Later in the chapter, you will simply be
you may find that you also need to review portions of
instructed to carry out many of the procedures you were
Use and Care of Hand Tools and Measuring Tools,
taught earlier in this chapter. Before you can fabricate
NAVEDTRA 12085, and Mathematics, Volume 1,
an item, you must have a plan and be able to read it.
Your plan may be a sketch, a drawing, or a blueprint.
Later on, you will be expected to make your own
USING LAYOUT TOOLS
sketches and drawings.
The tools you will use most often to lay out sheet
A SKETCH is a rough outline of the structure to be
metal jobs and patterns are the scratch awl, flat steel
fabricated, giving dimensions and details of the job to
square, circumference rule, straightedge, dividers,
be done. The sketch includes such information as angles
trammel points, prick punch, and center punch. When
to be used and the type of material required.
you make your practice layouts, you will probably be
A DRAWING is similar to a sketch, but it is made
restricted in the amount of sheet metal you can use. If
with mechanical drawing instruments and it is drawn to
at all possible, use template paper instead of metal. This
material has a rosin-coated surface that is well adapted