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R Series
Home Deep Groove Ball Bearings R Series

R133 Open Miniature Ball Bearing | Unshielded Ultra-Low Friction | 32.380×4.762×2.380mm

R133 Open Miniature Ball Bearing | Unshielded Ultra-Low Friction | 32.380×4.762×2.380mm

The R133 Open is a sub-miniature, single-row deep groove ball bearing specifically manufactured for environments that demand the absolute lowest possible friction torque. Built to imperial (inch) dimensions, this incredibly small bearing features a completely unshielded and unsealed design. By entirely exposing the inner raceways and rolling elements, the R133 Open eliminates the drag typically caused by protective shields. This unrestricted configuration allows for extreme free-spinning capabilities and rapid heat dissipation, making it an essential component for highly sensitive precision instruments housed in clean, debris-free environments.

R133 Miniature Deep Groove Ball Bearing 2.380 × 4.762 × 2.380 mm | Imperial (Inch) Series – Maximum Free-Spin Performance

Engineered to deliver flawlessly smooth rotation in microscopic spaces, the R133 Open excels in applications where starting torque must be kept to an absolute minimum. Because it lacks enclosures, it provides engineers with direct access for custom lubrication, allowing for the application of specialized ultra-low viscosity instrument oils or even dry-running setups. The optimized raceway geometry combined with the open design ensures hyper-responsive, fluid rotation, giving high-frequency micro-mechanisms the unhindered speed they require to operate accurately.

R133 Open Miniature Ball Bearing | Unshielded Ultra-Low Friction | 32.380×4.762×2.380mm

Comprehensive Applications

Ideal for specialized engineers, instrument technicians, and developers working on micro-assemblies that require zero-drag rotation within enclosed housings:

Precision Instruments & Metrology
  • High-Sensitivity Anemometers
  • Mechanical Gyroscopes and Navigation Systems
  • Micro-Dial Indicators
  • Precision Rotary Sensors
Micro-Motors & Actuators
  • Sub-Miniature Servo Motors
  • Compact Optical Drive Spindles
  • Small-Scale Robotics Joints
  • Low-Torque Stepper Motors
Hobbyist & Specialized Equipment
  • Professional Competition Yo-Yos
  • Scale Model Instrumentation
  • Micro-Pneumatic Tools
  • High-Speed Miniature Flow Meters

Key Performance Features

01. Open Configuration (Zero Shield Drag)

Unlike shielded or sealed bearings, the R133 features a completely open architecture. With no physical barriers creating rubbing or windage friction against the inner ring, the bearing achieves a near-zero friction coefficient. This design is perfect for systems enclosed in clean environments or oil baths, offering effortless maintenance, easy cleaning, and instant relubrication.

02. Premium GCr15 Chrome Steel Durability

Manufactured from high-carbon GCr15 Chrome Steel (equivalent to SAE 52100), all internal components are heat-treated to exact specifications. This ensures the balls and raceways possess the exceptional Rockwell hardness necessary to withstand continuous high-speed rotation, maintaining strict P5-level running accuracy over a long service life.

03. Ultra-Light Imperial Micro-Dimensions

Designed around an incredibly compact 3/32-inch bore and a slim 3/16-inch outer diameter, the R133 seamlessly integrates into the most confined spatial footprints. Weighing a mere fraction of a gram, it contributes virtually zero parasitic mass to your assembly, ensuring high-efficiency energy transfer in low-power, battery-operated micro-devices.

Technical Specifications

Bearing Type Single Row Deep Groove Ball Bearing
ISO Dimension Series R Series (Miniature Imperial / Inch)
Basic Designation R133
Suffix Options Open (No Shields/Seals)
Bore Diameter (d) 3/32" (2.380 mm)
Outer Diameter (D) 3/16" (4.762 mm)
Width (B) 3/32" (2.380 mm)
Material (Races & Balls) Chrome Steel (GCr15 / SAE 52100) or Stainless Steel (AISI 440C)
Precision Class Standard / P5 Grade Available
Cage Material Pressed Steel (ribbon type) or Polyamide
Dynamic Load Rating (Cʳ) Approx. 143 N
Static Load Rating (C₀ʳ) Approx. 45 N
Limiting Speed (Grease) 60,000 RPM
Limiting Speed (Oil) 70,000 RPM
Weight (approx.) 0.16 grams

Interchange Part Numbers

Cross-reference guide for equivalent global manufacturer part numbers:

  • NMB: RI-3332
  • SKF: R133
  • NSK: R133
  • NTN: R133
  • Barden: R133
  • KOYO: R133

Design & Configuration

Drawing on over 15 years of industry expertise, the technical team at Welink Bearing is dedicated to solving complex rotational challenges for our clients. The R133 Open provides the ultimate foundation for ultra-low torque requirements. Because of its open design, we can supply these bearings completely dry (rust-preventative only) or pre-lubricated with highly specialized instrument oils. We also offer tailored internal clearances (such as C3) to guarantee optimal performance for your specific operating temperatures and speeds.

"Achieve unparalleled rotational freedom with the R133 Open bearing—delivering zero-drag velocity, imperial precision, and exceptional responsiveness for your most sensitive micro-applications.”

Download Product Catalog (PDF)

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