SWBTEC
Excavator Swing Bearing Play
In order to accurately diagnose the clearance of the slewing bearing of the excavator, the first step is to stop the equipment on a solid level ground. This is very important. The ground is uneven and the measured data cannot be seen at all.
Then, firmly suck your magnetic table seat on the chassis (body), and then vertically top the dial gauge needle on the bottom surface of the outer ring of the slewing bearing (that is, the turntable). After everything is in place, reset the dial to zero first.
Next is the key operation: using the big arm and stick, use the bucket to gently press down on the ground, the purpose is to lift the entire car structure a little bit. At this time, you can read the deflection value on the dial gauge.
For the most common 20 to 40 ton excavators on the market, the maximum allowable value of this axial clearance is usually in the range of 1.5mm to 3.0mm (about 0.060 inches to 0.120 inches). If your measurement results exceed the specific tolerances given by the equipment manufacturer-or if you find metal particles in the grease-then I can responsibly tell you that the bearing has worn out beyond the safety limit and must be replaced immediately, otherwise it is only a matter of time before a catastrophic gear failure occurs.
Measurement Of Axial Clearance
Measuring the clearance (especially the axial clearance) of the rotary bearing is a fine job. It must be set with the right tool. The core tool is the dial gauge of the magnetic gauge seat. The essence of this process is to measure the amount of vertical movement between the upper structure and the lower chassis.
Preparation and Safety: Always ensure that the excavator is parked on firm, level ground. An uneven surface can cause serious deviations in readings.
Installation Instructions: The magnetic watch seat is firmly attached to the chassis (body). Remember, to be fixed in a stationary part.
Positioning Needle: The probe of the indicator is placed vertically on the bottom surface of the outer ring (rotary table) of the slewing bearing. Remember, it must be vertical so that the reading is accurate.
Dial Zeroing: Before applying any load, set the dial gauge to the zero position.
Apply Load: By operating the hydraulic system of the excavator (boom and stick), the bucket is gently pressed to the ground. Our goal is only to lift the upper structure slightly, just enough to allow the bearing surfaces to separate and expose the gap.
Reading The Deflection: Observe the dial gauge. The value it shows is the total axial clearance.
Standard Limits And Tolerances
Interpreting the measurement of excavator swing bearing play is key to deciding whether to repair or replace the component. Although the tolerances of different brands and models are different, there is a common judgment rule in the industry for standard 20 to 40 ton excavators:
Acceptable Range: New bearings or lightly used bearings, a little bit of activity is completely normal.
Warning Zone: When the clearance reading starts to approach the limits specified by the manufacturer, you have to be vigilant.
Scrap Limit: Generally speaking, the maximum allowable axial clearance is usually between 1.5mm and 3.0mm (0.060 “-0.120”). If your meter reading exceeds this specific tolerance range, it means that the internal raceway or rolling element has been severely degraded.
Continuing to operate an excavator with excessive clearance will seriously affect the stability and safety of the machine.
SLEWING BEARING
Rigorous Internal Quality Control、Expert Engineering & Innovative Design Capabilities、20 Years of Expertise in Slewing Bearing Manufacturing、Expert Engineering & Innovative Design Capabilities.
Diagnosing Wear Condition
In addition to physical measurements with a dial gauge, checking grease is the second diagnostic method that I personally value very much.
Metal Particles In Grease: During routine maintenance, or when measuring gaps, check the discharged waste grease by the way. If there are visible metal sequins or particles inside, this is a very clear signal that peeling or grinding has occurred inside the bearing. To be honest, at this stage, no matter what the dial indicator reads, this bearing is no longer good.
Risk Of Catastrophic Failure: The risk of catastrophic gear failure increases immediately as soon as the axial play is too large or metal particles appear in the butter. Excessive clearance may cause the teeth of the small gear and the large rotary gear ring to be misaligned or stuck, resulting in the teeth being knocked out, or even in extreme cases causing the upper structure to be detached.
Therefore, if your diagnosis confirms that the clearance of the slewing bearing of the excavator exceeds the range of 1.5mm -3.0mm, or metal contamination is found, the only safety measure is to replace it immediately.
Author：Dennis
Hi, I am a heavy equipment specialist with over a decade of experience in excavator maintenance. My expertise focuses on undercarriage parts and swing circle diagnostics. I am dedicated to helping operators and fleet managers extend machine life through precise wear analysis and maintenance strategies.
