CAT 521-9958 BEARING-SEM

CAT 521-9958 is a Caterpillar original equipment manufacturer (OEM) single-row tapered roller bearing for SEM (Shandong Machinery) loaders, corresponding to model 31313. It is commonly used in drive axle differentials, wheel-side reducers, or gearbox output shafts, and is compatible with loaders such as the SEM 655D/660D. It can withstand both radial and unidirectional axial loads, suitable for medium-to-heavy load and low-to-medium speed transmission conditions, ensuring stable operation of transmission components and reducing wear and failure risks.

Core Technical Parameters

Item Details
Part Model: CAT 521-9958 (SEM Matching, Replacement Model 31313) Single Row Tapered Roller Bearing

Material: Inner ring, outer ring, and rollers are made of 52100 chromium steel, hardened to HRC 60-64; cage is made of stamped steel plate, suitable for mineral oil/lithium-based grease lubrication, operating temperature -30℃ to 120℃, rated speed grease lubrication approx. 2800rpm, oil lubrication approx. 4200rpm

Key Dimensions: Inner diameter 75mm, outer diameter 140mm, width 39mm, cone angle approx. 12°, number of rollers 14, radial clearance 0.018-0.038mm, suitable journal tolerance h6, bearing housing tolerance H7

Compatible Models: SEM 655D/660D/816D/822D For loaders, this bearing is used to support the drive axle differential at both ends, the input shaft of the wheel-side reducer, and the output shaft of the gearbox.

Performance Characteristics: The separable structure facilitates installation and maintenance; the tapered roller design adapts to complex loads; the hardened material is fatigue-resistant and wear-resistant; the cage guides the rollers for stable operation, adapting to vibration conditions, ensuring transmission accuracy, and extending component life.

Core Functions and Structure:

Composite Load Bearing: The tapered design of the tapered rollers can simultaneously bear radial and unidirectional axial loads, adapting to the radial support and axial positioning requirements of the drive axle and gearbox shaft, preventing shaft movement and ensuring gear meshing accuracy.

High-Efficiency Transmission and Friction Reduction: The rollers and raceways have line contact, resulting in a low coefficient of friction, reducing transmission energy loss, adapting to medium- and low-speed heavy-load operating conditions, and simultaneously dissipating heat generated during operation, preventing bearing failure due to overheating.

Separable Structure for Convenient Maintenance: The inner ring and roller assembly can be separated from the outer ring, facilitating clearance adjustment during installation. Maintenance does not require complete disassembly of the transmission components, reducing maintenance difficulty and time costs.

Installation and Maintenance Points

Installation Specifications: Clean the journal, bearing housing, and bearing to remove oil and impurities. Inspect the bearing for cracks, roller damage, and cage deformation. Measure the dimensions of the journal and bearing housing to ensure the fit tolerances meet requirements.

Install using hot mounting (oil temperature ≤100℃) or cold mounting methods. Do not directly strike the bearing end face. After installation, adjust the radial clearance to 0.018-0.038mm to ensure smooth and unobstructed bearing operation.

After installation, apply clean lithium-based grease or inject suitable gear oil for pre-lubrication before startup to avoid dry friction.

Maintenance Recommendations: Every 1500 working hours, check: bearing operating temperature (normal ≤90℃), lubrication system oil pressure and level, and for any abnormal noises from the bearing. If abnormal temperature, abnormal noises, or oil leaks occur, promptly check the bearing wear and clearance.

When the radial clearance of a bearing exceeds 0.10 mm, or when damage such as pitting, peeling, or burning occurs on the raceway or rollers, it must be replaced. It is recommended to replace them in pairs to ensure the balance and stability of the transmission system.