CAT 558-5027 BEARING -SEM

CAT 558-5027 SEM is a Caterpillar original single-row tapered roller bearing assembly (SEM stands for Special Engineering Material/Sealing Fit). It is suitable for the final drive, differential, or gearbox output shaft of mini excavators and loaders, used to withstand radial and bidirectional axial combined loads. It is suitable for low-to-medium speed, impact-prone transmission scenarios, ensuring stable shaft positioning and power transmission, and reducing vibration and wear.

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Item Details
Part Model: CAT 558-5027 SEM (5585027) Tapered Roller Bearing Assembly, including inner ring, outer ring, rollers, and cage. SEM marking indicates materials and sealing design suitable for harsh operating conditions. No official direct replacement model.

Material: Bearing steel SAE 52100, inner/outer ring and rollers integrally hardened (HRC 60-64), cage is stamped low-carbon steel, suitable for gearbox oil/gear oil lubrication environments, impact resistant and wear resistant.

Key Dimensions: Inner diameter 60mm, outer diameter 100mm, width 23mm, taper 1:12, radial clearance 0.012-0.018mm, shaft fit tolerance h6, seat bore fit tolerance H7.

Compatible Models: CAT 305.5E2/306E2 mini excavators, 906M/907M loaders, 247B Skid steer loaders, used for final drive planetary carrier support, differential half-shaft bearings, and the rear end of the gearbox second shaft.

Performance Parameters: Rated dynamic load 62kN, rated static load 75kN, limiting speed 4500r/min (oil lubrication), operating temperature -30℃ to 120℃, compatible gear oil viscosity ISO VG 80-140.

Core Functions and Structure:

Combined load bearing: Tapered roller line contact structure with a large contact area, capable of simultaneously bearing radial and bidirectional axial loads on heavy-duty parts, preventing shaft bending deformation and movement, ensuring gear meshing accuracy and transmission efficiency.

Separable assembly: Separable inner ring design facilitates maintenance and operation in confined spaces; the cage precisely guides the rollers, reducing friction and noise, suitable for the frequent start-stop and load-sudden changes of construction machinery. Shaft Positioning and Buffering: Works with the outer ring and cage to achieve radial and axial positioning of the shaft system, suppressing vibration, absorbing impact loads, and extending the service life of the shaft, gears, and bearing assembly (Cat®…).

Installation and Maintenance Points
Installation Specifications: Clean the journal, housing, and bearing to remove oil and metal shavings. Check the journal surface roughness Ra≤0.8μm and housing roundness≤0.01mm.

Cold press-in (apply pressure to the inner/outer ring end faces using a special sleeve). Do not strike the rollers or cage. Adjust the preload (axial clearance 0.005-0.01mm) to ensure smooth operation, unobstructed lubrication channels, and pre-lubricate with gear oil.

Maintenance Recommendations: Every 1000 working hours, check: gear oil level/quality (no metal debris, no emulsification), bearing temperature ≤85℃. If the oil contains metal particles, disassemble and inspect for wear.

During a major overhaul, the bearing must be replaced, and the wear of the journal must be checked simultaneously. If the wear exceeds 0.05mm, the journal must be repaired or the entire shaft assembly must be replaced.