TM-5-3805-254-14-P-2
TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)
TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)
JUNE 1980
TM-5-3805-254-14-P-2 - Page 860 of 894
TRUCK SERVICE MANUAL
WHEELS, RIMS, TIRES
Fig. 4
emery or steel wool particles from drum after this
operation. More heavily damaged or out-of-round drums
should be ground or turned on brake drum lathe.
If depth of scoring, bellmouth or barrel shaping
exceeds .13 mm (.005"), measured with micrometer
across part or all of brake surface, drum should be
refinished. Reboring limits (see drum) must not be
exceeded and no heat checks, cracks or bluing is
evident.
Use a micrometer also to check for an out-of-
round drum. Make check by measuring drum brake
surface diameter at various points, 450 apart around
circumference. Eccentricity (out-of-round) should not
exceed .38 mm (.015") on diameter.
For older brake drums which do not show a
maximum diameter the drum must be discarded when
diameter is 3.05mm (.120") over original diameter.
Remember that each time brake drums are
turned, less metal remains to absorb the heat developed
by braking action.
Brake drums containing less metal will
operate at a higher temperature. As a result, brake fade,
slow recovery and erratic wear will be more noticeable.
Also, extremely high temperatures shorten lining life and
cause heat checks and cracks (Fig. 5) form on inner
surface of drums. These conditions will become
progressively worse until finally drums fail.
Fig. 5
To recondition a brake drum in a lathe (Fig. 6),
the drum must be mounted so that it is centered. Use
proper size cone to provide accurate centering. Turn
drum, taking only light cuts and remove just enough
material to clean up drum. Then grind the finished
surface if grinder is available or use emery cloth on a
straight piece of wood and polish the drum friction
surface.
NOTE: Brake drums that are otherwise
in good condition can be turned in a
lathe. However, it must be remembered
that recommended rebore limit for brake
drums over 35.6 cm (14") in diameter
must not be increased more than
2.03mm (.080") diameter (total cut) and
discarded at 3.05 mm (.120") over
normal diameter.
Brake drums should be cleaned thoroughly with
a steam cleaner or hot water.
Do not use a solvent
which leaves an oily residue. If inspection shows the
drums may be used without remachining, rub friction
surface with fine emery cloth or sandpaper to remove
any foreign deposits. If drum has been reconditioned,
clean friction surface with fine emery cloth or sandpaper
and wash. Next examine very carefully to see that no
metal chips remain in drum.
Fig. 6
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