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67 Series
Home Deep Groove Ball Bearings 67 Series

674 Open Ultra-Miniature Ball Bearing | High-Velocity Unshielded Design | 4×7×2.5 mm

674 Open Ultra-Miniature Ball Bearing | High-Velocity Unshielded Design | 4×7×2.5 mm

The 674 Open is a precision-engineered, single-row miniature ball bearing designed for applications where absolute minimal rotational resistance and maximum speed are the primary requirements. By removing the physical barriers of shields or seals, this 4x7x2.5 mm component allows for unrestricted lubrication flow and zero "drag," making it perfect for high-frequency vibration tools and precision instruments. With a featherweight mass of just 0.3 grams, the 674 open type excels in energy-sensitive systems where reducing mechanical friction is critical to extending battery life and improving motor response.

674 Deep Groove Ball Bearing 4x7x2.5 mm | 67 Series – Zero Torque & Maximum RPM

Designed for integration into clean, enclosed mechanical systems, this unshielded bearing offers the highest possible speed rating in its class. Capable of reaching up to 63,000 r/min when used with oil lubrication, the 674 Open avoids the heat buildup associated with contact friction. It is a vital component for micro-spindles and high-speed rotors, providing a seamless, whisper-quiet rotation under light radial and axial loads.

674 Open Ultra-Miniature Ball Bearing | High-Velocity Unshielded Design | 4×7×2.5 mm

Comprehensive Applications

Specially optimized for ultra-high-speed, clean-room, or oil-lubricated environments where compact dimensions are mandatory:

High-Speed Micro Rotors & Spindles
  • Miniature Dental and Surgical Turbines
  • High-RPM Micro Motor Armatures
  • Precision Gyroscopes and Balancing Units
  • Micro Centrifuge Internal Supports
Optical & Scanning Technology
  • High-Frequency Laser Scanning Mirrors
  • Precision Rotary Encoders
  • Compact Optical Inspection Gimbals
  • Automated Mirror Positioning Systems
Aerospace & Nano-Robotics
  • Satellite Reaction Wheel Assemblies
  • Ultra-Lightweight Robotic Joint Sensors
  • Micro-Actuator Internal Pivot Points
  • High-Precision Laboratory Automation

Key Performance Features

01. Zero-Friction Open Architecture

The unshielded design of the 674 Open ensures there is no contact friction between the rotating elements and outer closures. This results in the lowest possible starting and running torque, allowing for instantaneous acceleration and extreme efficiency in high-frequency applications.

02. Precision-Ground GCr15 Chrome Steel

Manufactured from high-purity GCr15 bearing steel, the raceways undergo advanced super-finishing processes. This ensures exceptional surface smoothness and fatigue life, delivering high-precision rotation even in the most demanding micro-mechanical assemblies.

03. Ultra-Miniature 2.5mm Width Profile

The 2.5mm cross-section empowers engineers to minimize the mechanical footprint of their devices without sacrificing structural rigidity. The ultra-small 4mm bore is ideal for the latest generation of handheld medical tech and micro-scale aerospace components.

Technical Specifications

Bearing Type Single Row Deep Groove Ball Bearing
ISO Dimension Series 6700 Series (Micro/Ultra-Thin Section)
Basic Designation 674
Suffix None (Open Type)
Bore Diameter (d) 4 mm
Outer Diameter (D) 7 mm
Width (B) 2.5 mm
Material (Races & Balls) Chrome Steel (GCr15 / SAE 52100)
Precision Class Standard / P5 Grade Available
Shield Material None
Dynamic Load Rating (Cʳ) 0.310 kN (310 N)
Static Load Rating (C₀ʳ) 0.115 kN (115 N)
Limiting Speed (Grease) 53,000 r/min
Limiting Speed (Oil) 63,000 r/min
Weight (approx.) 0.0003 kg (0.3 grams)

Interchange Part Numbers

Technical buyers can utilize the following manufacturer equivalents for cross-referencing:

  • SKF: 617/4
  • NSK: 674
  • FAG674
  • NTN: 674
  • KOYO: 674
  • NMB: L-740

Design & Configuration

The 674 Open bearing is the definitive choice for high-speed precision in protected, clean environments. Because it lacks integrated shields, it is highly receptive to customized oil or grease lubrication strategies tailored to your specific temperature or vacuum requirements. With over 15 years of manufacturing excellence, Welink Bearing provides the technical insight needed to optimize these micro-components for your most complex industrial challenges.

"Integrate the 674 Open miniature bearing to achieve peak rotational velocity and zero drag in your most space-constrained precision designs."

 

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674 Open Ultra-Miniature Ball Bearing | High-Velocity Unshielded Design | 4×7×2.5 mm

The 674 Open is a precision-engineered, single-row miniature ball bearing designed for applications where absolute minimal rotational resistance and maximum speed are the primary requirements. By removing the physical barriers of shields or seals, this 4x7x2.5 mm component allows for unrestricted lubrication flow and zero "drag," making it perfect for high-frequency vibration tools and precision instruments. With a featherweight mass of just 0.3 grams, the 674 open type excels in energy-sensitive systems where reducing mechanical friction is critical to extending battery life and improving motor response.

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The 679 Open is a precision-engineered, ultra-thin miniature ball bearing designed for high-velocity applications where rotational resistance must be kept to an absolute minimum. With a 9mm bore and a slim 14mm outer diameter, this "Open" type bearing features no seals or shields, allowing for the lowest possible starting torque and unrestricted rotational flow. This design is specifically intended for use in clean, controlled environments or within enclosed housings where external lubrication—such as oil baths or mist—is readily available to maintain the bearing’s internal components.

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The 678 Open is a high-precision, ultra-thin miniature ball bearing engineered for technical applications where minimizing rotational friction is the top priority. Featuring an 8mm bore and a compact 12mm outer diameter, this "Open" configuration lacks physical seals or shields, allowing the rolling elements to rotate with nearly zero starting torque. It is the ideal choice for high-speed systems operating within enclosed, debris-free environments—such as oil-mist lubricated housings or hermetically sealed instruments—where maximum mechanical efficiency and rapid heat dissipation are required.

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The 6702-ZZ is a specialized, ultra-lightweight deep groove ball bearing engineered for modern applications that demand minimal spatial footprint and maximum rotational efficiency. Featuring dual non-contact metal shields (ZZ), this model effectively retains premium factory grease while delivering significantly lower rotational friction than standard rubber-sealed variants. Measuring 15mm on the bore, an outer diameter of 21mm, and a remarkably slim 4mm width, the 6702-ZZ is an essential component for UAV mechanisms, gimbal stabilizers, and sophisticated medical devices where consistent, low-torque operation is critical.

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