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63 Series
Home Deep Groove Ball Bearings 63 Series

6321-ZZ Heavy-Duty Deep Groove Ball Bearing for Massive Industrial Loads | 105×225×49 mm

6321-ZZ Heavy-Duty Deep Groove Ball Bearing for Massive Industrial Loads | 105×225×49 mm

Engineered to withstand immense mechanical stress in harsh industrial environments, the 6321-ZZ is a rugged deep groove ball bearing from the heavy-duty 6300 series. Featuring a massive 105mm bore and fortified with dual pressed-steel shields (ZZ), this bearing acts as an impenetrable barrier against coarse debris, metallic dust, and particle ingress while securely housing its factory-filled lubricant. The non-contact nature of these metallic shields ensures that even at considerable dimensions, the 6321-ZZ operates with optimized heat dissipation and reduced rotational drag, making it an industrial powerhouse for large electric generators, heavy gearboxes, and mining equipment.

6321-ZZ Deep Groove Ball Bearing 105x225x49 mm | Extreme Load Capacity | Non-Contact Steel Shields

Manufactured to stringent ISO precision grades, this large-scale bearing features a remarkably thick cross-section and oversized rolling elements to accommodate extreme radial loads and substantial bidirectional axial forces. The integrated dual-metal shielding protects the deep, precision-honed raceways from contamination without the surface friction that rubber contact seals would create on such a large outer diameter. This meticulously calculated geometry prevents excessive thermal buildup, allowing the heavy-duty 6321-ZZ to deliver relentless, maintenance-free performance in demanding, high-torque electromechanical systems.

6321-ZZ Heavy-Duty Deep Groove Ball Bearing for Massive Industrial Loads | 105×225×49 mm

Comprehensive Applications

Engineered for rugged durability, extreme load tolerance, and large-shaft machinery:

Large Motors & Power Generation
  • Rotors and stators in massive industrial AC/DC electric motors
  • Shaft supports for wind turbine generators and commercial alternators
  • Heavy-duty industrial ventilation and exhaust blower systems
Heavy Industrial Machinery
  • Primary drivetrains in large-scale gearboxes and speed reducers
  • Drive rollers and heavy-duty conveyor systems in mining operations
  • Pulley and hoisting mechanisms in construction cranes
Processing & Manufacturing Equipment
  • Rollers in paper and pulp manufacturing mills
  • Heavy-duty crushing and screening equipment
  • Large automated sorting and material handling lines
Agricultural & Heavy Automotive
  • Drivetrain components in heavy agricultural tractors and combine harvesters
  • High-capacity industrial pump shafts and massive compressors
  • Heavy commercial vehicle transmission systems

Key Performance Features

01. Oversized Load-Bearing Geometry

With its commanding 225mm outer diameter and 49mm width, the 6321-ZZ boasts an exceptionally thick cross-section. This robust construction provides a massive dynamic load capacity, allowing it to easily absorb heavy shock loads and continuous high-torque stresses.

02. Low-Friction Deflection Shields (ZZ)

The twin steel shields offer superior defense against coarse industrial contaminants. By utilizing a non-contact design, these shields prevent the high-friction heat generation that is often problematic in large-diameter bearings, protecting the internal grease from thermal degradation.

03. Forged High-Carbon GCr15 Steel

Crafted from premium, ultra-pure GCr15 (SAE 52100) chrome steel, the massive inner/outer rings and oversized balls undergo advanced, deep heat treatments. This rigorous metallurgical process ensures maximum structural rigidity, exceptional wear resistance, and long-term fatigue strength under heavy loads.

Technical Specifications

Bearing Type Single Row Deep Groove Ball Bearing
ISO Dimension Series 6300 Series (Heavy Duty)
Basic Designation 6321
Suffix ZZ (Double Steel Shields)
Bore Diameter (d) 105 mm
Outer Diameter (D) 225 mm
Width (B) 49 mm
Material (Races & Balls) Chrome Steel (GCr15 / SAE 52100)
Precision Class Standard / P5 Grade Available
Shield Material Cold-Rolled Pressed Steel
Dynamic Load Rating (Cʳ) 174.0 kN
Static Load Rating (C₀ʳ) 137.0 kN
Limiting Speed (Grease) 2,800 r/min
Limiting Speed (Oil) 3,400 r/min
Weight (approx.) 8.05 kg

Interchange Part Numbers

Directly replaces the following equivalent heavy-duty manufacturer parts:

  • SKF: 6321-2Z
  • NSK: 6321ZZ
  • FAG: 6321-2Z
  • KOYO: 6321ZZ
  • TIMKEN: 6321ZZ
  • NTN: 6321ZZ

Design & Configuration

The standard 6321-ZZ is pre-lubricated with a premium, heavy-duty industrial grease formulated to withstand high pressures and typical operating temperatures. Because massive bearings like the 6321 often operate in environments prone to significant thermal expansion and heavy shaft fits, this bearing is frequently supplied with a C3 radial internal clearance to prevent seizing. If your equipment operates in highly corrosive environments, specialized anti-corrosion coatings can be discussed. For applications exposed to extreme moisture, sludge, or direct debris impact, we highly recommend inquiring about our fully sealed 6321-2RS configuration.

"Combining immense load-carrying capacity with a massive 105mm bore, the 6321-ZZ delivers relentless durability and structural integrity for the world's most demanding industrial machinery."

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