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178
FIAT·850 PASSENGER CARS
Fig. 295 _ Turning brake drum on lathe.
1. Cutter. - 2. lathe M. 1004.
~
3. Brake drum. - 4. Drum
holding
spacer
Next, reface linings with refacer Ap. 5031 as
shown in fig. 297.
BRAKE DRUMS
Examine brake drums:
if
scores or out-oi-round
are detected turn them on lathe M. 1004 (fig. 295).
After skimming. lap drums using lapping fixture
M. 1005 which must be inserted on lathe machine
(fig. 296).
Lapping should be made with with very fine
grade stones in order to eliminate any roughness
left by lathe cutter during turning operation.
Maximum oversize allowed in respect of standard
diameter of drums after turning and lapping:
Fig. 296 • lapping brake drum.
1. Brake drum. - 2. Lapping machine M. 1005. - 3. lathe M. 1004·
standard diameter
7.2915" to 7.3032"
(185.24 to 185.53 rom)
oversize . . . . .
.0315" (0.8 rom)
Drum centering and balance conditions should
not be affected as a result of skimming operation.
Do not exceed
dnun
oversize limit as otherwise
both the strength and braking power of drwn may
be impaired.
Adjusting Shoe-to-Drum Clearance.
Brake shoes are of the self-centering type and
therefore no alignment problem is met with them.
As a matter of fact
I
brake shoes are setting
automatically at center on pedal depression; this
condition is obtained thanks to the adoption, in the
place of the conventional anchor pin. of a spring
guided pin (figures 290 and 291) allowing for slight
side movements of shoes, which are supported on
a lower plate (figures 293 and 294). Brakes shoes,
under the impending hydraulic pressure from wheel
Fig. 297 • Refacing brake shoe linings.
1.
Shoe lining .• 2. Carriage operating bar, - 3. Slone of refacer
Ap. 5031.
cylinders, are caused to expand and move for such
a seating as their working area will adhere to the
drum face at all points.
Prior to adjusting the shoe-to-drum clearance,
operate the brakes with running vehicle to ensure
centering of brake shoes, especially when they
have been renewed.
Then proceed as follows at each wheel:
_ jack up the vehicle on the side where work is
needed;
- depress the brake pedal fully to have brake
shoes contact the drum;
keep the pedal
in
down position and
turn
the
nuts of adjusting cams outward to the last stop;
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