CAT 522-8339 Bushing (SEM)

CAT 522-8339 is a straight-tube steel-backed copper alloy bushing from Caterpillar for SEM (Shandong Machinery) loaders and excavators. It is used for radial high-load support of the working device pin joints and can be used with 235-9767 retaining ring assemblies and 584-7993 YM sleeve bearings. It features wear resistance, impact resistance, and self-lubricating properties and is suitable for Cat® Parts in dusty and vibrating environments. The following is structured technical and application information:

Core Technical Parameters

Item Details
Basic Attributes
Model 522-8339, Straight Cylindrical Bushing, Steel Back + CuSn8 Bronze Layer (Bronze Layer Thickness 1.2-1.8 mm, Surface Tin Plating 0.005 mm, Porosity 15-20%, Contains Solid Lubricant), Single Weight Approx. 0.68 kg, Operating Temperature -30℃ to +150℃, Load Type: Radial High Load, Friction Coefficient ≤0.08 (Oil Lubrication), Lubrication Method: Grease Lubrication (Recommended Cat 2V-9822 Grease), Design Life ≥8000 Hours (Normal Operating Conditions)

Key Dimensions
Inner Diameter 40 mm (Tolerance 0/-0.015 mm, Fitting Pin H7 Tolerance), Outer Diameter 50 mm (Tolerance +0.012/0 mm, Fitting Seat Hole H7 Tolerance), Length 40 mm (Tolerance 0/-0.12 mm), Wall Thickness 5 mm diameter, 1×45° chamfer at both ends, inner hole surface roughness Ra≤0.05 μm, outer circle cylindricity≤0.01 mm, end face parallelism≤0.01 mm
Compatible Models and Accessories: Compatible with SEM 652D/653D loaders (boom-rocker pin), SEM 816D excavators (stick-bucket pin), with matching 235-9767 retaining ring assembly, 584-7993 YM sleeve bearing, 474-9675 O-ring
Rated Load: Radial rated dynamic load Cr=50 kN, radial rated static load Cor=120 kN, allowable linear velocity ≤1.5 m/s (grease lubrication) / ≤3 m/s (oil lubrication), impact load ≥25 kN, ultimate pressure ≥200 kN MPa
Structural and Performance Advantages
The steel backing provides high-strength support, while the copper alloy layer offers excellent wear resistance and self-lubrication. The tin-plated surface enhances corrosion resistance and initial lubrication, making it suitable for dusty and vibrating Cat® Parts applications.

The cylindrical structure adapts to compact installation spaces, facilitating cold-press installation. It allows for greater elastic deformation, accommodates a wider range of shaft diameter tolerances, and effectively prevents loosening under vibration conditions, ensuring reliable component positioning.

The flangeless design reduces axial space occupation, making it suitable for multi-component tandem installations and reducing the risk of assembly interference.

Installation and Maintenance Points
Before installation, clean the inner and outer surfaces of the bushing, pin, and seat hole. Inspect for cracks, rust, and deformation. Measure the dimensions of the seat hole (50 mm, H7 tolerance) and pin (40 mm, h7 tolerance) to ensure an interference fit of 0.010-0.025 mm.

Cold-press installation is adopted. Apply pressure evenly to the bushing end face using a special press; do not strike the copper alloy surface. After installation, check for smooth rotation; there should be no jamming or abnormal noise. Axial movement should be ≤0.05 mm, and the coaxiality between the inner hole and the pin should be ≤0.02 mm.

Maintenance and Replacement: Check wear and lubrication condition every 1000 hours. If the inner diameter wear is >0.2 mm or the copper layer is peeling off, replace immediately. It is recommended to replace it simultaneously with the pin and seals to ensure joint connection accuracy and sealing effect.