JLG 600SC_660SJC Service Manual - Manual (Page 35)

SECTION 3 - TURNTABLE
3120898 – JLG Lift – 3-5
2. Check the turntable to bearing. Attach bolts as fol-
lows:
a. Elevate the fully retracted boom to 70 degrees
(full elevation).
b. At the positions indicated on Figure 3-4. try and
insert the .0015" feeler gauge between the bolt
head and hardened washer at the arrow indi-
cated position.
c. Lower the boom to horizontal and fully extend
the boom.
d. At the position indicated on Figure 3-4. try and
insert the .0015" feeler gauge between the bolt
head and hardened washer at the arrow indi-
cated position.
Wear Tolerance
1. From the underside of the machine, at rear center,
with the boom fully elevated and fully retracted, as
shown in A, Figure 3-6., Swing Bearing Tolerance
Boom Placement, using a magnetic base dial indica-
tor, measure and record the distance between the
swing bearing and turntable. (See Figure 3-5., Swing
Bearing Tolerance Measuring Point.)
2. At the same point, with the boom at horizontal and
fully extended, and the tower boom fully elevated as
shown in (Figure 3-6., Swing Bearing Tolerance
Boom Placement) B, using a magnetic base dial
indicator, measure and record the distance between
the swing bearing and turntable. (See Figure 3-5.,
Swing Bearing Tolerance Measuring Point.)
3. If a difference greater than 0.057 in. (1.40 mm) is
determined, the swing bearing should be replaced.
4. If a difference less than 0.057 in. (1.40 mm) is deter-
mined, and any of the following conditions exist, the
bearing should be removed, disassembled, and
inspected for the following:
a. Metal particles in the grease.
b. Increased drive power required.
c. Noise.
d. Rough rotation.
5. If bearing inspection shows no defects, reassemble
and return to service.
IMPORTANT
THE SWING BEARING IS ONE OF THE MOST CRITICAL POINTS
ON AN AERIAL LIFT. IT IS HERE THAT THE STRESSES OF LIFT-
ING ARE CONCENTRATED, AT THE CENTER OF ROTATION.
BECAUSE OF THIS, PROPER MAINTENANCE OF THE SWING
BEARING BOLTS IS A MUST FOR SAFE OPERATION.
Swing Bearing Replacement
1. Removal.
a. From Ground Control station, operate the boom
adequately to provide access to frame opening
or, if equipped, to rotary coupling.
NEVER WORK BENEATH THE BOOM WITHOUT FIRST ENGAGING
BOOM SAFETY PROP OR PROVIDING ADEQUATE OVERHEAD
SLING SUPPORT AND/OR BLOCKING.
b. Attach an adequate support sling to the boom
and draw all slack from sling. Prop or block the
boom if feasible.
c. From inside turntable, remove mounting hard-
ware which attach rotary coupling retaining yoke
brackets to turntable.
IMPORTANT
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
d. Tag and disconnect the hydraulic lines from the
fittings on the top of the rotary coupling. Use a
suitable container to retain any residual hydrau-
lic fluid. Immediately cap lines and ports.
.0015" Feeler Gauge
Figure 3-4. Swing Bearing Bolt Feeler Gauge Check
SWING
BEARING
FRAME REF.
TURNTABLE REF.
MEASURING
POINT
Figure 3-5. Swing Bearing Tolerance Measuring Point