TM-9-2330-335-14-P
SEMITRAILER, TACTICAL, BREAKBULK/CONTAINER TRANSPORTER, 22-1/2 TON, RESET M871R, M871A1R AND M871A2R
TECHNICAL MANUAL; FIELD AND SUSTAINMENT MAINTENANCE MANUAL (INCLUDES REPAIR PARTS AND SPECIAL TOOLS LIST)
SEPTEMBER 2008
TM-9-2330-335-14-P - Page 603 of 640
0106-3
TM 9-2330-335-14&P
0106
BRAKE DRUM SERVICE INFORMATION - CONTINUED
Turning the Brake Surface
000106
It may be desirable to turn or resurface the braking surface to remove small heat checks or other surface defects. The following
should be noted when turning:
a.
When resurfacing a drum, allow at least 0.040 in. under the maximum diameter for additional wear. This usually
means the drum may be turned a total of 0.080 in. over the brake surface diameter of a new brake drum.
CAUTION
Do not turn or wear a brake drum beyond the maximum diameter stamped or cast on the
brake drum.
b.
The maximum diameter or discard diameter is the maximum diameter to which the brake drum may be turned or
worn and still be unusable. If any portion of the brake surface exceeds the maximum diameter it must be discarded.
The maximum diameter is 0.120 in. over the nominal new diameter unless stated otherwise stated on the casting. The
maximum diameter cast into the back plate portions of the brake drum supersedes all published information.
Determining Replacement
000106
1.
Replacement of the brake drum is required if any of the following conditions exist:
a.
Brake drum is cracked.
b.
The brake surface is heat checked, grooved, or worn beyond the re-bore limit of 0.080 in., or maximum diameter.
c.
The back plate is cracked.
d.
The bolt holes are elongated.
e.
Brake drum is known to have been severely overheated.
f.
Brake drum is out-of-round.
2.
When selecting a Webb replacement drum, the manufacturer’s name and part number are helpful. If this information is not
available, a replacement drum can be selected by comparing dimensions. Figure 2 shows the dimensions required to
determine the existence of a replacement drum. If all the dimensions shown are not available, you must provide at least
the following dimensions from the previous page to make a selection:
a.
Brake Face Diameter
b.
Overall Depth of Drum
c.
Brake Surface Flat
d.
Bolt Circle Diameter
e.
Pilot Diameter
f.
Bolt Holes: Number and Size
Example:
New drum diameter
16.500
Re-bore allowance
00.080
Diameter after re-
bore limit is reached
16.580
Wear allowance
0.040
Maximum diameter
16.620
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