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52
Maintenance
HC-7X NEXSTAR
Rotation Bearing Replacement
All bearings wear over time, including the main rotation bearing of the crane. There are no precise rules
for replacing the main rotation bearing because of many variable factors. There are common symptoms
during crane operation that may indicate rotation bearing wear. These include:
1. Excessive noise.
2. Rough rotation.
3. Increase drive power required to rotate.
4. Metal particles in grease.
Replace the Bearing If :
5. Any noticeable cracking in the bearing housing.
6. Damage to internal teeth.
7. Excessive axial play is present. See Axial Play Allowance Check Procedure.
Never try to repair a rotation bearing. For a replacement bearing contact
your local authorized distributor.
Axial Play Allowance Procedure
1. Raise the boom to the maximum angle and measure the clearance between base plate and the rotation
bearing with a dial or filler gauge.
2. Lower the boom to the horizontal position and measure the clearance between the base plate and the
rotation bearing with a dial indicator or feeler gauge.
3. If the difference between the two measurements exceeds the specification, replace the bearing.
4. Rotate crane 45°, then repeat steps 1 and 2 until you reach 360° of rotation.
!
WARNING
Crane Model Axial Play Allowance Rotation Bearing
Replacement Kit
EC-2X, EHC-3.2, HC-3.2, EHC-4 1.5 mm 320878010
EHC-5, EHC-6, HC-5, HC-6, HC-
7, HC-8, 8406H, HC-9
1.6 mm 480023010
HC-7x, HC-8x 0.1 mm 479200220
HC-10, HC-12S 1.8 mm 372064010
HC-12, HC-14 2.3 mm 470001010