Chapter 5 General Reference 119
Turntable Bearing Inspection
Turntable bearings may experience wear. One of the following conditions may indicate turntable
bearing wear:
1 Metal particles present in the bearing lubricant.
2 Increased drive power required to rotate the crane.
3 Noise emitting from the bearing during rotation.
4 Rough rotation.
5 Uneven or excessive wear between the pinion gear and turntable gear.
If one or more of the above conditions exists, further inspection may be required. Limits are
measured in “TILT” which is dependent on the internal clearances of the bearing. TILT is the
most practical determination of a bearings' internal clearance once mounted on a crane. You
can measure the tilt using the Turntable Bearing Tilt Test. (see "Turntable Bearing Tilt Test" on
page 119)
Periodic readings indicating a steady increase in TILT may be an indicator of bearing wear. Note
that a bearing found to have no raceway cracks or other structural irregularities should be reassembled and
returned to service.
Turntable Bearing Tilt Test
1 Place crane in vertical position.
2 Set a dial indicator at 0 on the pinion cover plate at back side of mast.
3 Lower crane to the horizontal position.
4 Check and record the dial indicator change. It should not exceed the tilt measurement noted
in the chart below.
5 Return the crane to the vertical position. The dial indicator should return to 0.
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