Torch brazing and soldering are discussed in
Steelworker, volume 1, chapter 6. This section deals
only with joining sheet-metal seams by either metal
screws or rivets.
Different types of metal screws are available for
sheet-metal work. The most common type in use is the
MACHINE SCREW. Machine screws are normally
made of brass or steel. They will have either a flathead
or a roundhead and are identified by their number size,
threads per inch, and length; for example, a 6 by 32 by
1 inch screw indicates a number 6 screw with
32 threads per inch and 1 inch in length.
SELF-TAPPING SHEET-METAL SCREWS are
another common type of screw. Most screws of this
type will be galvanized and are identified by their
number size and length. These screws form a thread
as they are driven (fig. 2-81), as the name implies.
THREAD-CUTTING SCREWS (fig. 2-82) are
different from self-tapping screws in that they actually
cut threads in the metal. They are hardened and are used
to fasten nonferrous metals and join heavy gauge sheet
Figure 2-81.Self-tapping sheet-metal screws
Figure 2-83.Drive screws.
DRIVE SCREWS (fig. 2-83) are simply
hammered into a drilled or punched hole of the proper
size to make a permanent fastening.
Rivets are available in many different materials,
sizes, and types. Rivets, made of steel, copper, brass,
and aluminum, are widely used. Rivets should be the
same material as the sheet metal that they join.
TINNERS RIVETS of the kind shown in figure
2-84 are used in sheet-metal work more than any other
type of rivet. Tinners rivets vary in size from the
8-ounce rivet to the 16-pound rivet. This size
designation signifies the weight of 1,000 rivets. If
1,000 rivets weigh 8 ounces, each rivet is called an
8-ounce rivet. As the weight per 1,000 rivets increases,
the diameter and length of the rivets also increase. For
example, the 8-ounce rivet has a diameter of 0.089
inch and a length of 5/32 inch, while the 12-pound
rivet has a diameter of 0.259 inch and a length of 1/2
inch. For special jobs that require fastening several
layers of metal together, special rivets with extra, long
shanks are used. Table 2-1 is a guide for selecting
rivets of the proper size for sheet-metal work.
Figure 2-84.Tinners rivets.
Table 2-1.Guide for Selecting Rivet Size for Sheet-Metal
Figure 2-82.Thread-cutttng screws.