CAT 398-9799 BEARING AS.

CAT 398-9799 is a Caterpillar slewing bearing assembly (large turntable bearing assembly), suitable for mini excavators such as the 306E2. It supports the upper structure’s slewing and transmits torque, serving as a core load-bearing component of the slewing mechanism. The following is precise technical and application information:

Core Technical Parameters
Item Details
Part Model: CAT 398-9799 (3989799) Slewing Bearing Assembly, weighing approximately 180 kg, suitable for the 306E2 mini excavator, includes inner ring, outer ring, rolling elements, cage, seals, and lubrication system

Core Materials: Outer Ring / Inner Ring (50Mn alloy structural steel, tempered hardness HB 220-260, tooth surface hardened HRC 58-62); Rolling Elements (GCr15 bearing steel, hardness HRC 60-64); Cage (ZL104 cast aluminum, tensile strength ≥240 MPa); Seal (Nitrile rubber) NBR (Oil and Wear Resistant)

Key Dimensions: Outer diameter 1250 mm, Inner diameter 980 mm, Height 105 mm, Module 8, Number of teeth 150, Pressure angle 20°, Rolling element diameter 30 mm, Number of rolling elements 80, Bolt hole distribution circle diameter 1120 mm, Bolt holes 20 (diameter 24 mm)

Rated Parameters: Operating temperature -30℃ to +120℃, Rated static load 2500 kN, Rated dynamic load 1000 kN, Suitable swing speed ≤10 rpm, Suitable overturning moment ≤800 kN・m, Bolt preload torque 1800 N・m

Suitable Working Conditions: Suitable for the swing mechanism of small and medium-sized excavators, bearing radial load, axial load and overturning moment; suitable for dusty and vibrating working conditions; requires regular lubrication.

Compatible Models: CAT 306E2 mini excavator, also compatible with… Models 305.5E2 (partial serial numbers), 307E2, etc.

Accessories: Compatible bolts 7X-0495 (M24×180), grease nipple 1U-8878, sealing ring 453-2166, bolt anti-loosening washers 8T-4125

Core Functions and Structural Features:

Integral Load-Bearing: Four-point contact ball structure, simultaneously bearing radial and axial loads and overturning moments, suitable for excavator swing conditions, transmitting the weight of the upper structure and operating torque.

Sealing Protection: Double-lip seal + dustproof lip design prevents mud, sand, and moisture from entering, protecting the rolling elements and tooth surfaces, suitable for dusty outdoor conditions.

High-Efficiency Lubrication: Annular lubrication groove + radial oil holes (20 evenly distributed) ensure even grease coverage of the rolling elements, reducing swing wear and extending service life.

Easy Installation: Flange connection, secured with 20 bolts, locating pins for auxiliary installation, coaxiality ≤0.1 mm, tooth flank clearance 0.15-0.25 mm after installation.

Installation and Maintenance Points
Installation Specifications: Clean the mounting surface and bolt holes, removing burrs and oil contaminants. Inspect the bearing for cracks, tooth surface damage, and seal integrity.

Use locating pins for positioning. Pre-tighten the bolts symmetrically in stages (3 times, torques of 600 N·m, 1200 N·m, and 1800 N·m respectively). After installation, ensure smooth rotation without jamming or abnormal noise, and that the clearance meets requirements.

After installation, fill with NLGI 2 lithium-based grease and run for 10 minutes, then top up with more grease.

Maintenance Recommendations: Top up grease every 200 working hours. Check bolt torque and tooth surface wear every 800 working hours. Replace the bearing if tooth surface wear >0.5 mm or rolling element pitting occurs.

Avoid prolonged overload rotation to prevent fatigue spalling of the tooth surface and damage to the rolling elements.