The hardness gap occurs in the process of raceway inductive hardening and is located between the end and the beginning of the hardening. These areas must be placed in the area of least load. Ideally at zero load when installing slewing bearing.
The position of the hardness gap on each of the slewing ring can be told as follows:
Slewing Bearing | Internal gear type | External gear type | Non Gear type |
Inner ring | S marking | Filler plug | S marking or filler plug |
Outer ring | Filler plug | S marking | S marking or filler plug |
Before fastening, use a feeler gauge to check whether the surface of the slewing bearing is completely supported by the mounting structure. If this is not the case, the support surfaced of the mounting structure must be reworked. Please follow the sequence pattern below to install bolts:
Before fastening, use a feeler gauge to check whether the surface of the slewing bearing is completely supported by the mounting structure. If this is not the case, the support surfaced of the mounting structure must be reworked. Please follow the sequence pattern below to install bolts:
Tighten all fasteners lightly, and tighten to a specified value using a properly calibrated torque
Wrench, hydraulic devices are advisable. When tightening the whole bolt circle, ensure a uniform tightening torque. The recommend bolt tightening torque values are listed in the table below:
Bolt Thread size | Bore Dia mm DIN/ISO 273 | Tightening Torque at μ=0.14Nm | |
Bolt class 8.8 | Bolt Class 10.9 | ||
M12 | 14 | 79 | 117 |
M14 | 16 | 126 | 184 |
M16 | 17.5 | 193 | 279 |
M18 | 20 | 270 | 387 |
M20 | 22 | 387 | 558 |
M24 | 26 | 666 | 954 |
M27 | 3330 | 990 | 1395 |
M30 | 33 | 1350 | 1890 |
UNC |
| Grade 5 | Grade 8 |
UNC5/8”-11 | 18 | 180 | 260 |
UNC3/4”-10 | 21 | 320 | 460 |
UNC7/8”-9 | 25 | 520 | 730 |
UNC1”-8 | 27.5 | 770 | 1100 |
UNC1 1/8”-7 | 32 | 970 | 1560 |
UNC 1 1/4”-7 | 35 | 1370 | 2190 |
UNF |
| Grade 5 | Grade 8 |
UNF5/8”-18 | 18 | 210 | 290 |
UNF3/4”-16 | 21 | 360 | 510 |
UNF7/8”-14 | 25 | 580 | 820 |
UNF1”-12 | 27.5 | 860 | 1210 |
UNF1 1/8”-12 | 32 | 1100 | 1760 |
UNF 1 1/4”-12 | 35 | 1520 | 2440 |
The slewing bearing should be rotated during tightening process as this will indicate the development of any tight spots, the cause of which must be investigated.
The bolt torque should be checked before machine is finally operated to check for any loss of pre-load due to the structure settling.
Pinion Installation
The pinion should be located approximately at 90°of the major loading axis. Adjust the driving pinion to maximum eccentric point of the gear ring, usually with green or red paint covering 2 or 3 teeth. The backlash of the slewing bearing gear and pinion must be within the limits of the calculated values or minimum at 0.05 x module. When several pinions are used,each one must be adjusted to the same conditions. During test, make sure good alignment of the pinion and of the slewing bearing axes permits a satisfactory contact cross all gear width. Before running, lubricate the slewing bearing gear and pinion gear.
Running Test
After final tightening of all fasteners:
Rotate the ring for at least 3 turns. Recheck the backlash value on the gear mesh over one full revolution. Measure the total deflection under a know load. The checked point should be maked.It is advisable to register these values in a maintenance logbook specific to the machine.
Deflection measurement under load mounted slewing bearing
Operating process:
Place a measuring device between the two rings as close as possible to the raceway on the main load axis: precision grade 0.1mm minimum.
Calibrate to zero under a known load. Apply a measured load. Read the deflection value at the
point considered. Repeat this measurement in the previously marked points. Take into account the deflection of the support structure and the fasteners elongation corresponding to the instrument position.
