CAT 521-9955 BEARING-SEM

CAT 521-9955 SEM is a Caterpillar genuine double-row self-aligning roller bearing (SEM represents the standard tolerance and surface finish grade adapted for specific operating conditions). It is suitable for heavy-duty transmission and travel systems with a certain degree of angular deviation. The following are precise original specifications and application information, excluding replacement parts Cat®…

Core Technical Parameters

Item Details
Part Model: CAT 521-9955 SEM (Double Row Self-Aligning Roller Bearing, SEM Standard Grade)

Product Type: Double row symmetrical self-aligning roller bearing with cage, suitable for heavy-load, low-speed, and angularly misaligned applications.

Material: Rings and rolling elements are made of AISI 52100 high-carbon chromium bearing steel, hardened to 60–64 HRC; cage is made of stamped brass, SEM grade surface roughness Ra ≤ 0.8 μm.

Key Dimensions: Inner diameter 100 mm (3.937 in), outer diameter 180 mm (7.087 in), width 46 mm (1.811 in), fillet radius r1=2.5 mm, r2=3 mm

Rated Parameters: Radial rated dynamic load 195 kN, radial rated static load 200 kN; suitable pressure ≤ 35 MPa, operating temperature -30℃ ~ +120℃, linear velocity… ≤ 0.8 m/s
Physical Properties: Density 7.85 g/cm³, Elastic Modulus 208 GPa, Coefficient of Thermal Expansion 12.5×10⁻⁶/℃, Allowable Angular Deviation ≤ 2°
Single Weight: Approx. 4.2 kg (9.26 lbs)
Lubrication Design: Outer ring with annular lubrication groove and 2 radial oil holes, suitable for centralized lubrication systems, ensuring uniform lubrication between rollers and raceways.
Tolerance Standards: Inner diameter tolerance P6, outer diameter tolerance P6, SEM-level dimensional consistency, suitable for the precision assembly requirements of heavy-duty equipment.
Structure and Core Characteristics:
Double-row self-aligning structure: Symmetrical double-row roller design automatically compensates for angular deviations (≤ 2°) between the shaft and housing, adapting to installation errors or shaft deflection conditions, reducing edge stress.

Heavy-duty Adaptation Optimization: AISI 52100 bearing steel quenching treatment, double-row rollers share the load, strong radial load-bearing capacity, suitable for heavy-duty parts such as transmission systems and traveling mechanisms. SEM-level compatibility: Balances performance and cost with standard tolerances and surface treatments, suitable for the general heavy-duty conditions of Caterpillar’s medium and large-sized equipment, offering strong versatility and convenient maintenance.

Stable lubrication design: Annular lubrication grooves combined with radial oil holes ensure efficient grease coverage of the contact surface, reducing friction and wear, and extending bearing life.

Brass cage advantages: Stamped brass cages offer high strength and good thermal conductivity, suitable for low-speed, heavy-duty conditions, preventing roller jamming and improving operational stability.

Compatible models and application scenarios:

Compatible equipment: Cat®® 336D2/349D2 excavators, 980K/982M loaders, 770G/772G mining trucks, and other heavy-duty components such as final drives, differentials, and steering knuckles.

Core applications: Provides heavy-duty radial support, compensates for angular deviations, absorbs shocks and vibrations, and ensures stable operation of the transmission and travel systems, suitable for harsh working conditions such as mining and infrastructure projects.