JLG 660SJ Service Manual - Manual (Page 93)

SECTION 3 - CHASSIS & TURNTABLE
3120840 – JLG Lift – 3-43
Wear Tolerance.(S & A Models)
1. From the underside of the machine, at rear center,
with the boom fully elevated and fully retracted, as
shown in (Figure 3-29., Swing Bearing Tolerance
Boom Placement (S Models) and Figure 3-28.,
Swing Bearing Tolerance Boom Placement (A Mod-
els), using a magnetic base dial indicator, measure
and record the distance between the swing bearing
and turntable. (See Figure 3-27., Swing Bearing Tol-
erance 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 3-29., Swing Bearing Tolerance
Boom Placement (S Models) and Figure 3-28.,
Swing Bearing Tolerance Boom Placement (A Mod-
els) - 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 3-27., Swing Bearing Toler-
ance Measuring Point)
3. If a difference greater than 1.40 mm is determined,
the swing bearing should be replaced.
4. If a difference less than 1.40 mm is determined, 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.
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
FRAME REF.
TURNTABLE REF.
MEASURING
POINT
Figure 3-27. Swing Bearing Tolerance Measuring
Point