MOTOR TRUCK SERVICE MANUAL
BODIES AND CABS
area is depressed below the surface of the surrounding
area and the depression then filled with fiber glass or
plastic putty.
ALUMINUM ALLOYS
Sheet Alloys (Skin),
Aluminum, like many metals, is not generally used in
a "pure" form. In order to achieve certain desirable
properties, it is alloyed with other metals. In some
applications, specifications call for a class of aluminum
alloys containing magnesium as the principal alloying
ingredient. Those commonly used in sheet form are
5052, 5154, 5086, 5454; while alloys 5154, 5356 and
5554 are the commonly used welding electrodes.
Fig. 4. Showing use of SE-2127 Portable White Line
Magnetic Inspection Tool. The crack area is
Structural Alloys
dusted with a special white powder which clearly
Rolled and extruded structural shapes used in
indicates the crack length when the magnetic
underframing and other applications may be alloy 6061,
field across the crack is generated.
6062 or 6063. These are heat treatable alloys having
both magnesium and silicon as alloying ingredients.
They are readily weldable to each other and to the
aluminum-magnesium series of alloys with 5154 and
5356 welding electrode and wire.
Crack Repair
Where cracks are to be repaired in the aluminum
sheet or skin, they must be prepared properly before
welding; however, it should be determined before making
the repair whether some additional reinforcement in the
crack area is required to prevent further problems.
Simple crack repair is as follows:
1. Locate the extent of the crack area or length. Often
the fine line of the entire crack length is not visible.
Use a dye penetrant to aid in locating the crack
length. Brush a small amount of the dye over the
suspected crack area. The dye will expose the
suffice. Do not run the chisel past the drilled holes at the
crack. If the SE-2127 Portable White Line Magnetic
crack ends (Fig. 3).
Inspection Tool is available, it can be used to expose
cracks in aluminum. This tool utilizes a magnetic
4. After the crack is widened, the work must be cleaned
field in conjunction with a white powder to indicate
on both sides if possible. Use a stainless steel brush
the crack.
Complete detailed instructions for
and make certain that all dirt, grease or paint has
operating the SE-2127 are included with the tool
been removed.
(Fig. 4).
2. After locating the crack and its extent, drill one 1/8"
5. Apply the weld to the prepared area by
hole at each end of the crack to prevent further
progress of the crack. (Fig. 5).
3. Using a thin chisel, open the crack a small amount
by driving down against the crack along its full
length. Do not widen the crack excessively. About
1/16" width will
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