CAT 521-9876 BUSHING–SEM

CAT 521-9876 is a Caterpillar original equipment straight sleeve bushing for SEM (Shandong) loaders and other models. It is suitable for hinged parts such as booms and rocker arms, used to reduce friction between the pin and the mounting hole and to withstand radial loads. The following is pure original data and does not include information on replacement parts.

Core Technical Parameters (Raw Data)

Item Details
Basic Attributes
Model 521-9876, Type: Straight Steel Sleeve Bushing (no flange, no oil groove), suitable for SEM loaders and some CAT construction machinery articulated structures, Single weight 0.85 kg, Working temperature -40℃ to +120℃, Suitable for hydraulic oil and grease media, used in heavy-duty low-speed oscillating conditions, extending the life of articulated components.

Key Dimensions (Metric/Imperial)
Inner diameter 50.8 mm (2.0 in, tolerance ±0.02 mm), Outer diameter 63.5 mm (2.5 in, tolerance ±0.03 mm), Overall length 63.5 mm (2.5 in, tolerance ±0.1 mm), Wall thickness 6.35 mm, Fitting pin diameter 50.8 mm, Mounting hole diameter 63.5 mm, Mounting depth ≥63.5 mm

Performance Parameters
Material: 4140 Alloy steel (surface hardened, hardness HRC 58-62), radial load capacity ≥120 kN, wear life ≥7000 hours, friction coefficient ≤0.12 (lubricated state), impact strength ≥75 J/cm², no significant rust after ≥240 hours of salt spray testing, suitable for oscillating conditions with speeds ≤8 rpm.

Structure and Compatibility Characteristics

Compatible with SEM Models: Designed specifically for SEM 650, 652B, 653, 658D loaders, adaptable to the hinge joints of the boom and frame, rocker arm and connecting rod. Replacing old bushings restores hinge clearance and improves operational stability.

Oil-less Design: No internal or external lubrication grooves or oil holes; relies on the equipment’s centralized lubrication system for oil supply. Compatible with forced lubrication hinge structures, ensuring uniform lubrication and reducing friction loss.

Integral Forging Process: Forged from 4140 alloy steel with surface hardening, possessing both high hardness and toughness, capable of withstanding heavy loads and impacts, suitable for harsh working conditions in engineering machinery.

Installation and Maintenance Points (Original Data)

Installation: Clean the mounting holes and pins (free from oil, rust, and burrs). Use cold pressing or hot fitting methods (heat the mounting holes to 100-120℃). Hammering is prohibited. After installation, the bushing end face should be flush with the mounting hole, with a coaxiality tolerance ≤0.05 mm and a radial clearance of 0.08-0.12 mm, ensuring the pin rotates freely without jamming.

Maintenance: Check lubrication every 500 hours and replenish with lithium-based grease regularly (5-8 g each time). Replace immediately when the bushing inner diameter wears ≥0.2 mm, or when surface cracks or peeling occur, to prevent excessive wear on the pins and mounting holes.