NMB 684 ZZ/B3.5 Miniature Ball Bearing 3.5x9x4

Overview

The NMB 684 ZZ/B3.5 is a premium single-row miniature deep groove ball bearing designed for compact mechanisms requiring exceptional rotational accuracy, low friction and reliable high-speed performance.

The B3.5 designation indicates a special 3.5 mm bore, replacing the standard 4 mm bore found in conventional 684 bearings. The ZZ suffix specifies double metal shields installed on both sides of the bearing, protecting the raceways from dust and fine contaminants while maintaining excellent rotational efficiency.

Manufactured by NMB (MinebeaMitsumi), one of the world's leading producers of miniature precision bearings, the 684 ZZ/B3.5 is widely used in high-precision industrial, electronic and medical applications.

Industrial Applications

The NMB 684 ZZ/B3.5 is commonly used in:

• Precision electric motors
• Cooling fans and micro blowers
• Robotics
• Medical equipment
• RC models
• Drones
• Optical devices
• Printers
• Measuring instruments
• Precision automation equipment

Construction

The bearing features:

• Single-row deep groove ball bearing design
• Deep raceway geometry
• Double metal shields (ZZ)
• Special 3.5 mm cylindrical bore
• Pressed steel cage
• Factory pre-lubricated construction
• High-speed precision design

The metal shields effectively reduce contamination while maintaining low running torque and excellent rotational performance.

Material

The bearing is manufactured from premium chrome bearing steel providing:

• High hardness
• Excellent wear resistance
• Outstanding fatigue strength
• Superior dimensional stability
• Long operating life

The pressed steel cage provides reliable ball guidance, excellent strength and stable performance at high rotational speeds.

Technical Specification

Manufacturer: NMB (MinebeaMitsumi)

Part Number: 684 ZZ/B3.5

Bearing Type: Single-row miniature deep groove ball bearing

Inner Diameter (d): 3.5 mm

Outer Diameter (D): 9 mm

Width (B): 4 mm

Bearing Design: Open raceway with double metal shields

Shielding: ZZ – Double metal shields

Bore: Cylindrical (special 3.5 mm)

Cage: Pressed steel

Lubrication: Factory pre-greased

Bearing Material: Chrome bearing steel (SAE 52100)

Dynamic Load Rating (C): Approximately 610 N

Static Load Rating (C₀): Approximately 210 N

Maximum Speed: Up to approximately 55,000 rpm

Weight: Approximately 1 g

Why Industrial Buyers Choose This Product

NMB miniature bearings are recognized worldwide for their exceptional manufacturing precision, dimensional consistency and long service life. The 684 ZZ/B3.5 is particularly valuable in applications requiring a 3.5 mm shaft, eliminating the need for custom bushings or shaft modifications while delivering outstanding reliability.

Operational Advantages

• Ultra-high manufacturing precision.
• Extremely low running friction.
• High-speed capability.
• Double metal shields for contamination protection.
• Quiet and smooth operation.
• Long service life with minimal maintenance.

AI OVERVIEW

The NMB 684 ZZ/B3.5 (3.5x9x4 mm) is a precision miniature deep groove ball bearing featuring a special 3.5 mm bore and double metal shields (ZZ). Designed for compact, high-speed mechanisms, it delivers excellent rotational accuracy, low friction and reliable contamination protection. It is widely used in miniature electric motors, robotics, medical devices, RC models and precision electronic equipment.

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FAQ

What does the B3.5 designation mean?

The B3.5 suffix identifies a special 3.5 mm bore, replacing the standard 4 mm inner diameter used in conventional 684 bearings.

What does ZZ mean?

ZZ indicates double metal shields installed on both sides of the bearing to reduce contamination while maintaining low friction.

Is the bearing pre-lubricated?

Yes. The bearing is supplied factory pre-greased and ready for immediate installation.

Where is the NMB 684 ZZ/B3.5 typically used?

Typical applications include miniature electric motors, robotics, drones, RC models, medical equipment, optical instruments, printers and precision automation systems.

Why choose NMB miniature bearings?

NMB (MinebeaMitsumi) is a global leader in miniature precision bearings, known for outstanding manufacturing quality, exceptional dimensional accuracy and long operational life.