Product Overview

The NMT 628/6-2Z is a double-shielded, single-row miniature deep groove ball bearing. With a 6 mm bore, 13 mm outer diameter, and 5 mm width, this bearing is manufactured from high-quality bearing steel with a stamped metal cage, equipped with non-contact metal shields on both sides (2Z) and pre-filled with high-quality grease. It integrates maintenance-free sealing, compact design, high-speed capability, and precision rotational accuracy into a single package, accommodating radial and bidirectional axial loads simultaneously.

 

The bearing offers a basic dynamic load rating of 0.88 kN (880 N) and a static load rating of 0.35 – 0.42 kN (350 – 420 N) . It achieves a reference speed of 110,000 r/min and a limiting speed of 53,000 r/min. The bearing weighs only 0.0021 – 0.0025 kg (2.1 – 2.5 g)  with an operating temperature range of -30°C to 120°C. The tolerance class is P0 (Normal/ABEC 1) with CN radial clearance. Bore tolerance -0.008mm to 0, OD tolerance -0.008mm to 0.

 

The 2Z double metal shields are the key design feature – non-contact shields effectively prevent contaminant ingress while adding no extra resistance or heat generation, and the bearing comes pre-lubricated from the factory for maintenance-free operation. The compact 6×13×5 mm dimensions make it ideal for space-constrained miniature applications. The synergy of maintenance-free sealing, compact design, high-speed capability, and precision rotational accuracy makes this bearing the ideal bearing solution for miniature high-speed equipment.

 

Model Code Decoding – Understanding NMT 628/6-2Z

Code Meaning

628 Basic model – 6 mm bore, 13 mm OD, 5 mm width

/6 Bore size code, indicating 6 mm bore diameter

-2Z Shield on both sides – non-contact metal shields on both sides

Core Value: The 2Z double metal shields effectively prevent contaminant ingress while the non-contact design adds no extra resistance or heat generation. The compact 6×13×5 mm dimensions of the 628 series make it ideal for space-constrained applications. The P0 precision class combined with CN radial clearance ensures reliable operation. The low-friction design and optimised internal geometry deliver a reference speed of 110,000 r/min and a limiting speed of 53,000 r/min. The synergy of high-speed capability, compact design, and maintenance-free sealing makes this bearing the ideal precision bearing solution for miniature high-speed equipment.

 

Core Performance Advantages

1. Double Metal Shields – Maintenance-Free, Extended Life

The bearing features non-contact metal shields on both sides (2Z) that effectively prevent dust and other contaminants from entering the bearing interior, while the non-contact design avoids friction between the shield and the inner ring – adding no extra resistance or heat generation. The bearing is pre-filled with high-quality grease at the factory and is maintenance-free – no washing or relubrication is required. This ensures stable temperature performance even at 53,000 r/min high speeds, while the integral sealing significantly prolongs bearing service life.

 

2. Compact Miniaturisation – 6×13×5 mm

With compact dimensions – 6 mm bore, 13 mm outer diameter, and 5 mm width – this bearing can be easily integrated into space-constrained precision equipment. Weighing only 2.1 – 2.5 g, it is particularly suitable for miniature devices with space and weight requirements, such as precision instruments, miniature motors, and optical scanners.

 

3. 53,000 r/min High-Speed Performance – Industry-Leading

This bearing achieves a reference speed of 110,000 r/min and a limiting speed of 53,000 r/min. The low-friction design and optimised internal geometry ensure stable operation and low heat generation at high speeds. This speed level makes it the ideal choice for high-speed miniature motors, precision instrument spindles, and other high-speed miniature devices.

 

4. Deep Groove Design – Bidirectional Load Capacity, Excellent Versatility

Deep groove ball bearings feature a simple structure, wide versatility, and low friction. This bearing can accommodate radial loads and bidirectional axial loads simultaneously, providing excellent load capacity in miniaturised designs. With a dynamic load rating of 0.88 kN (880 N) and static load rating of 0.35 – 0.42 kN (350 – 420 N) , it meets the load requirements of most miniature applications.

 

5. P0 Normal Precision (ABEC 1) + CN Radial Clearance – Versatility and Reliability Combined

This bearing features P0 normal precision class (ABEC 1) and CN normal radial internal clearance. Bore tolerance -0.008mm to 0, OD tolerance -0.008mm to 0. This combination ensures reliable operation in the vast majority of general miniature applications, while facilitating easy installation and maintenance.

 

6. Ultra-Lightweight – Only 2.1 – 2.5 Grams

The bearing weighs only 0.0021 – 0.0025 kg (2.1 – 2.5 g) . The extremely low rotating mass effectively reduces centrifugal loads and inertia moments at high speeds.

 

7. Wide Operating Temperature Range

This bearing operates within a temperature range of -30°C to 120°C, capable of adapting to various demanding environments from cold storage to high-temperature processing.

 

8. RoHS and REACH Compliant

This bearing is compliant with RoHS and REACH environmental standards, ensuring safe use even in regions with strict environmental regulations.

 

9. Clear Performance Specifications

 

Parameter Value

Bore d 6 mm

Bore Tolerance -0.008mm to 0

Outer Diameter D 13 mm

OD Tolerance -0.008mm to 0

Width B 5 mm

Width Tolerance -0.12mm to 0

Chamfer r₁,₂ min. 0.15 mm

Dynamic Load Rating C 0.88 kN (880 N)

Static Load Rating C₀ 0.35 – 0.42 kN

Fatigue Load Limit Pu 0.015 kN

Reference Speed 110,000 r/min

Limiting Speed 53,000 r/min

Ball Material Bearing Steel

Ring Material Bearing Steel

Cage Material Stamped Metal

Seal Type Double Metal Shields (2Z)

Tolerance Class P0 (Normal/ABEC 1)

Radial Clearance CN (Normal)

Lubrication Pre-filled Grease

Weight 0.0021 – 0.0025 kg (2.1 – 2.5 g)

Temperature Range -30°C to 120°C

Typical Applications

The NMT 628/6-2Z, with its double-shielded maintenance-free design, compact dimensions, and high-speed capability, covers an exceptionally wide range of high-end miniature applications:

 

Small Precision Motors – stepper motors, DC micromotors, servo motors

 

Precision Instruments – measuring devices, optical scanners, chromatography products

 

Medical Devices – dental handpieces, surgical tools, laboratory equipment

 

Optical Equipment – laser scanners, rotating mirrors, optical encoders

 

Semiconductor Manufacturing Equipment – precision wafer processing, chip packaging

 

Office Automation Equipment – printers, scanners

 

Household Appliances – internal combustion engines, home appliances

 

Industrial Machinery – gearboxes, instrumentation, agricultural machinery, construction machinery

 

Automotive Applications – transmissions, clutch systems

 

Consumer Products – inline skates, yo-yos, etc.

 

Automation Equipment – lightweight robotic arms, precision-guided mechanisms

 

Important Installation Notes

✅ This bearing features double metal shields (2Z) and comes pre-filled with high-quality grease – maintenance-free. Ready to install out of the box – no washing or relubrication required.

 

✅ Ensure shaft and housing fits comply with P0 grade requirements. Chamfer dimension r₁,₂ min. 0.15 mm.

 

✅ Due to the compact size (only 2.1 – 2.5 g), use specialised miniature bearing installation tools and take extra care to avoid excessive force or impact.

 

✅ Installation in a clean environment is recommended to prevent contaminant ingress that could affect high-speed performance.

 

⚠️ This bearing has no preload setting – if paired configurations or specific preload are required, adjust based on application requirements.

 

⚠️ This bearing has no lubrication groove and no relubrication feature – the shielded design is lubricated for life, requiring no relubrication.

 

NMT Quality Commitment

Japan NMT (Enmutī) has deep expertise in the precision bearing industry, with breakthroughs in material purification, process refinement, scenario customisation, and intelligent upgrading, transforming precision bearings into core solutions addressing pain points across multiple industries. The NMT 628/6-2Z bearing is manufactured to strict Japanese quality standards – from ring material (high-purity bearing steel) and rolling elements to superfinishing processes. The combination of double metal shields (2Z), compact miniature design, P0 precision class (ABEC 1), and CN radial clearance makes this bearing the flagship precision bearing in the NMT miniature bearing series – offering the perfect balance of maintenance-free sealing, high speed, and precision performance.

 

Choose NMT 628/6-2Z for:

 

✅ Double metal shields – maintenance-free, extended life

 

✅ Compact miniaturisation – 6×13×5 mm, only 2.1 – 2.5 g

 

✅ 53,000 r/min high-speed performance – industry-leading

 

✅ Deep groove design – bidirectional load capacity, low friction, low noise

 

✅ Stamped metal cage – low friction, high speed

 

✅ Wide temperature range – -30°C to 120°C

 

✅ RoHS and REACH compliant

 

✅ Factory pre-lubricated – ready to install

 

✅ Japanese precision manufacturing quality