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63 Series
Home Deep Groove Ball Bearings 63 Series

6311-ZZ Heavy-Duty Deep Groove Ball Bearing | 55×120×29 mm for Industrial Machinery & Large Motors

6311-ZZ Heavy-Duty Deep Groove Ball Bearing | 55×120×29 mm for Industrial Machinery & Large Motors

Built to endure rigorous operating conditions and heavy mechanical stress, the 6311-ZZ is a premium medium-to-heavy series deep groove ball bearing. Equipped with dual pressed-steel shields (ZZ), it provides an excellent barrier against industrial debris and particulate contamination while securely retaining the factory-applied lubricant. Because the metal shields are non-contacting, this bearing minimizes friction and heat generation, making it the optimal solution for high-load, 55mm shaft applications such as large electric motors, industrial gearboxes, and agricultural equipment.

6311-ZZ Deep Groove Ball Bearing 55x120x29 mm | High Load Capacity | Non-Contact Seals

Manufactured to strict ISO precision standards, this bearing utilizes a robust internal architecture designed to accommodate substantial radial loads, as well as moderate axial loads in both directions. The integrated steel shields ensure ongoing protection of the hardened raceways and rolling elements without adding mechanical drag. This efficient design prevents the excessive thermal expansion often associated with contact seals, allowing the 6311-ZZ to maintain smooth, continuous operation in demanding, maintenance-free industrial setups.

6311-ZZ Heavy-Duty Deep Groove Ball Bearing | 55×120×29 mm for Industrial Machinery & Large Motors

Comprehensive Applications

Engineered for stability, high load capacities, and continuous heavy-duty rotation:

Large Electric Motors & Generators
  • Stator and rotor supports in high-output industrial motors
  • Wind turbine generators and renewable energy equipment
  • Heavy-duty traction motors for railway and transit
  • Industrial power generators and alternators
Power Transmission & Gearboxes
  • Main shafts in heavy industrial gear reducers
  • Conveyor belt drive systems and mining pulleys
  • Mechanical power presses and stamping machinery
  • Industrial clutches and heavy-duty drivetrains
Agricultural & Construction Equipment
  • Tractor PTO (Power Take-Off) shafts and drivetrains
  • Combine harvester threshing mechanisms
  • Earthmoving equipment and heavy excavators
  • High-capacity vibrating screens and crushers
Fluid Handling & HVAC Systems
  • Large-scale industrial water and chemical pumps
  • High-volume ventilation fans for mining and tunneling
  • Commercial centrifugal compressors
  • Blower systems for industrial furnaces

Key Performance Features

01. Exceptional Radial Load Capability

Designed with a substantial 29mm width and large rolling elements, the 55x120x29mm geometry is optimized for the 6300 medium/heavy series. It effortlessly absorbs aggressive shock loads and heavy continuous radial forces, maximizing the service life of large mechanical assemblies.

02. Dual Metal Shielding for Extended Lifespan

By utilizing twin pressed-steel shields (ZZ), the bearing actively repels dust, metal shavings, and environmental debris. This non-contact defense mechanism prevents the friction-induced wear typical of rubber seals, keeping operating temperatures lower and preserving the integrity of the internal grease over a longer lifecycle.

03. Forged GCr15 Bearing Steel

Manufactured from high-purity, vacuum-degassed chrome steel (GCr15), the inner/outer rings and ball bearings are subjected to advanced heat treatment processes. This results in superior Rockwell hardness, exceptional resistance to metal fatigue, and highly reliable, low-vibration performance under heavy stress.

Technical Specifications

Bearing Type Single Row Deep Groove Ball Bearing
ISO Dimension Series 6300 Series (Medium / Heavy Series)
Basic Designation 6311
Suffix ZZ (Double Steel Shields)
Bore Diameter (d) 55 mm
Outer Diameter (D) 120 mm
Width (B) 29 mm
Material (Races & Balls) Chrome Steel (GCr15 / SAE 52100)
Precision Class Standard / P5 Grade Available
Shield Material Pressed Steel
Dynamic Load Rating (Cʳ) 71.5 kN
Static Load Rating (C₀ʳ) 45.0 kN
Limiting Speed (Grease) 6,300 r/min
Limiting Speed (Oil) -
Weight (approx.) 1.37 kg

Interchange Part Numbers

Directly replaces the following manufacturer parts:

  • SKF: 6311-2Z
  • NSK: 6311ZZ
  • FAG: 6311-2Z
  • KOYO: 6311ZZ
  • TIMKEN: 6311ZZ
  • NTN: 6311ZZ

Design & Configuration

The standard 6311-ZZ comes pre-lubricated with high-quality, oxidation-resistant grease suitable for a wide range of industrial temperatures. Because heavy machinery often generates significant operating heat, we frequently supply this model with a C3 internal clearance to safely accommodate thermal expansion of the steel. If your application involves direct exposure to heavy moisture, splashing water, or extreme dust, please inquire about our fully sealed 6311-2RS rubber-contact variants.

"Combining exceptional load-carrying strength with maintenance-free shielding, the 6311-ZZ ensures peak operational uptime for heavy-duty industrial infrastructure."

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