CAT 521-9959 BEARING-SEM

CAT 521-9959 is a Caterpillar original equipment manufacturer (OEM) tapered roller bearing for SEM (Shandong Electric Machinery) models. It is primarily used in heavy-duty transmission components such as drive axles and final drives, providing precise radial and axial positioning. The following are OEM specifications and application information; replacement parts are not included.

Core Technical Parameters

Item Details
Part Model: CAT 521-9959 (SEM Dedicated Tapered Roller Bearing, Single Row, Separable Outer Ring)

Material: Inner Ring / Outer Ring / Roller: High Carbon Chromium Bearing Steel (GCr15), Cage: Stamped Steel Plate, Heat Treatment Hardness HRC 60-64, Roller Surface Carburizing Depth 0.8-1.2 mm

Key Dimensions: Inner Diameter 70 mm (2.756 in), Outer Diameter 150 mm (5.906 in), Width 38 mm (1.496 in), Number of Rollers: 16, Roller Diameter 14.5 mm, Taper Angle 12°30′

Performance Parameters: Dynamic Rated Load 112 kN, Static Rated Load 138 kN, Limiting Speed ​​3800 rpm (Grease Lubricated), Operating Temperature -40℃ to +120℃

Single Weight: Approx. 2.85 kg (6.28 kg) (lbs)

Tolerance Standards: Inner diameter tolerance P5 (+0.012/0 mm), outer diameter tolerance P6 (0/-0.015 mm), width tolerance ±0.15 mm

Sealing Type: Open type, compatible with original equipment manufacturer (OEM) oil seals, requires regular lubrication

Structure and Core Characteristics

Tapered Roller Structure: Single-row tapered roller design, capable of simultaneously bearing radial and unidirectional axial loads, suitable for drive axles, final drives, and other applications subjected to both radial and axial forces. The tapered surface contact ensures uniform load distribution, improving load-bearing capacity and lifespan.

High-Rigidity Cage: The stamped steel cage is high-strength and lightweight, stably guiding roller movement and preventing roller tilting and jamming. Suitable for medium- and high-speed operation, with strong impact resistance.

Precision Heat Treatment: GCr15 bearing steel undergoes quenching and tempering treatment, achieving a balance between hardness and toughness. Carburizing treatment on the roller surface enhances wear resistance, suitable for heavy-load and vibration environments in harsh engineering machinery conditions.

Separable outer ring design: Facilitates disassembly and replacement during installation and maintenance, adapting to rapid on-site repair needs and reducing downtime.

Compatible Models and Application Scenarios

Compatible Equipment: Loaders such as the SEM652D, SEM655D, and SEM660D, as well as drive axle main reducers, wheel-side reducers, and final drives in CAT and SEM combined models.

Core Applications: Installed at the output end of the drive axle differential, wheel-side reducer shaft, and final drive input shaft, it supports the rotating shaft and transmits loads, restricts radial and axial movement of the shaft, ensures stable operation of the transmission system, and is suitable for heavy-duty material loading, earthmoving operations, and other similar conditions.