Swing Bearing; Turntable Bearing Mounting Bolt Condition Check; Wear Tolerance - JLG 660SJ Service And Maintenance Manual

SECTION 3 - CHASSIS & TURNTABLE

3.8 SWING BEARING

Turntable Bearing Mounting Bolt Condition Check

NOTE: This check is designed to replace existing bearing bolt
torque checks on JLG Lifts in service. This check must be
performed after first 50 hours of machine operation and
every 600 hours of machine operation thereafter. If any
bolts are missing or loose, replace missing or loose bolts
with new bolts and torque to value specified in torque
chart after lubricating bolt threads with loctite #271. After
replacing and retorquing bolt or bolts, recheck all bolts for
looseness.
1. Check frame to bearing. Attach bolts as follows:
a. Elevate fully retracted boom to 70° (full elevation).
b. Try and insert a 0.0015" feeler gauge between bolt
head and hardened washer at position shown in Fig-
ure 3-61.
c. Make sure 0.0015" feeler gauge will not fit under
bolt head to bolt shank.
d. Swing turntable 90° and check some selected bolts
at new position.
e. Continue rotating turntable at 90° intervals until a
sampling of bolts are checked in all quadrants.
2. Check turntable to bearing. Attach bolts as follows:
a. Elevate fully retracted boom to 70° (full elevation).
b. try and insert a 0.0015" feeler gauge between bolt
head and hardened washer at positions shown in
Figure 3-61.
c. Lower boom to horizontal and fully extend boom.
d. Try and insert the 0.0015" feeler gauge between bolt
head and hardened washer at position shown in Fig-
ure 3-61.
Figure 3-61. Swing Bearing Bolt Feeler Gauge Check
3-44

Wear Tolerance

SWING BEARING IS ONE OF THE MOST CRITICAL POINTS ON AN AERIAL LIFT. IT
IS HERE STRESSES OF LIFTING ARE CONCENTRATED, AT CENTER OF ROTATION.
BECAUSE OF THIS, PROPER MAINTENANCE OF SWING BEARING BOLTS IS A
MUST FOR SAFE OPERATION.
1. From underside of machine, at rear center, with boom
fully elevated and fully retracted, as shown in Figure 3-
63., Swing Bearing Tolerance Measurement Location &
Boom Placement A, using a magnetic base dial indicator,
measure and record distance between swing bearing
and turntable as shown in Figure 3-62., Swing Bearing
Tolerance Measuring Point.
2. At the same point, with boom horizontal and fully
extended, and tower boom fully elevated as shown in -
Swing Bearing Tolerance Boom Placement B, using a
magnetic base dial indicator, measure and record dis-
tance between swing bearing and turntable as shown in
Figure 3-62., Swing Bearing Tolerance Measuring Point.
3. If difference is greater than 0.079 in. (2.00 mm), replace
swing bearing.
4. If difference is less than 0.079 in. (2.00 mm) and any of
the following conditions exist:
a. Metal particles in grease.
b. Increased drive power required.
c. Noise.
d. Rough rotation.
5. Remove, disassemble, and inspect bearing. If bearing
inspection shows no defects, reassemble and return to
service.
Figure 3-62. Swing Bearing Tolerance Measuring Point
– JLG Lift – 3121298