Product Overview

The NMT W 638/5 R-2Z is a flanged (R), double-shielded (2Z) single-row stainless steel miniature deep groove ball bearing. With a 5 mm bore, 11 mm outer diameter, and 5 mm width, this bearing features an integral flange on the outer ring with a flange outer diameter of 12.5 mm and flange thickness of 1 mm. Manufactured entirely from stainless steel (rings, balls, and cage all stainless steel) with a stainless steel stamped cage, equipped with non-contact metal shields on both sides (2Z)  and pre-filled with high-quality grease, it integrates flanged convenience, maintenance-free sealing, high corrosion resistance, compact design, and precision rotational accuracy into a single package, accommodating radial and bidirectional axial loads simultaneously.

 

The bearing offers a dynamic radial load rating of 91 lbf (0.403 kN)  and a static radial load rating of 32 lbf (0.143 kN) , with a fatigue load limit of 0.006 kN. It achieves a reference speed of 120,000 r/min and a limiting speed of 60,000 r/min. The bearing weighs only 0.002 kg (2 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, width tolerance -0.12mm to 0.

 

The integral flange (R) design is the most prominent structural feature of this bearing – the outer ring flange (flange OD 12.5 mm) enables direct axial location without the need for additional retaining rings or circlips, significantly simplifying installation and saving axial space. The 2Z metal shields effectively prevent contaminant ingress while adding no extra resistance or heat generation. The all-stainless steel construction (AISI 440C equivalent) provides excellent corrosion resistance and chemical resistance. The synergy of flanged convenience, maintenance-free sealing, high corrosion resistance, compact design, and precision rotational accuracy makes this bearing the ideal bearing solution for miniature high-speed equipment.

 

Core Performance Advantages

1. Integral Flanged Design (R) – Easy Installation, Space Saving

The integral flange on the outer ring is the most prominent structural advantage of this bearing:

 

Simplified axial location: Flange outer diameter 12.5 mm, directly mates with the housing face – no additional retaining rings or circlips required

 

Space saving: Eliminates the need for locating shoulders on the shaft or in the housing

 

Quick installation: Direct press-fit into the housing completes location, significantly reducing assembly time and cost

 

Enhanced system rigidity: Precise flange location provides excellent axial positioning and system rigidity

 

2. 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 60,000 r/min high speeds, while significantly extending maintenance intervals.

 

3. All-Stainless Steel Construction – High Corrosion Resistance, Extended Life

Manufactured entirely from stainless steel (rings, balls, and cage all stainless steel), this bearing provides excellent corrosion resistance and chemical resistance. In humid, corrosive, or high-cleanliness environments, stainless steel bearings effectively resist rust and chemical attack, significantly extending service life. This makes them particularly suitable for food processing machinery, medical devices, marine applications, and chemical processing equipment with strict cleanliness and corrosion resistance requirements.

 

4. Compact Miniaturization – 5×11×5 mm

With compact dimensions – 5 mm bore, 11 mm outer diameter, and 5 mm width – this bearing can be easily integrated into space-constrained precision equipment. Flange outer diameter 12.5 mm. Weighing only 2 g, it is particularly suitable for miniature devices with space and weight requirements, such as precision instruments, miniature motors, and optical scanners.

 

5. 60,000 r/min High-Speed Performance – Industry-Leading

This bearing achieves a reference speed of 120,000 r/min and a limiting speed of 60,000 r/min. The low-friction design and optimized internal geometry（recess diameter d₂ ≈ 6.2 mm, groove diameter D₂ ≈ 9.9 mm）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, dental handpieces, and other high-speed miniature devices.

 

6. 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 miniaturized designs. With a dynamic load rating of 91 lbf (0.403 kN) and static load rating of 32 lbf (0.143 kN) , it meets the load requirements of most miniature applications.

 

7. 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, width tolerance -0.12mm to 0. This combination ensures reliable operation in the vast majority of general miniature applications, while facilitating easy installation and maintenance.

 

8. 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.

 

9. RoHS and REACH Compliant

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

 

10. Clear Performance Specifications

 

Parameter Value

Bore d 5 mm

Bore Tolerance -0.008mm to 0

Outer Diameter D 11 mm

OD Tolerance -0.008mm to 0

Width B 5 mm

Width Tolerance -0.12mm to 0

Flange Outer Diameter 12.5 mm

Flange Thickness 1 mm

Recess Diameter d₂ ≈ 6.2 mm

Groove Diameter D₂ ≈ 9.9 mm

Dynamic Radial Load 91 lbf (0.403 kN)

Static Radial Load 32 lbf (0.143 kN)

Fatigue Load Limit 0.006 kN

Reference Speed 120,000 r/min

Limiting Speed 60,000 r/min

Ball Material Stainless Steel

Ring Material Stainless Steel

Cage Material Stainless Steel

Flange Type Integral Flange (R)

Seal Type Double Metal Shields (2Z)

Tolerance Class P0 (Normal/ABEC 1)

Radial Clearance CN (Normal)

Lubrication Pre-filled Grease

Weight 0.002 kg (2 g)

Temperature Range -30°C to 120°C

Typical Applications

The NMT W 638/5 R-2Z, with its flanged convenience, maintenance-free sealing, high-corrosion-resistance stainless steel material, and compact precision design, covers an exceptionally wide range of high-end miniature applications:

 

Small Precision Motors – stepper motors, DC micromotors, cooling fans

 

Medical Devices – dental handpieces, surgical tools, laboratory equipment

 

Precision Instruments – measuring devices, optical scanners, chromatography products

 

Automation Equipment – lightweight robotic arms, precision-guided mechanisms

 

Food Processing Machinery – corrosion-resistant miniature transmission mechanisms

 

Marine and Chemical Industries – equipment exposed to seawater, steam, and other corrosive fluids

 

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

 

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

 

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

 

Important Installation Notes

✅ This bearing features an integral flange on the outer ring (R) with flange outer diameter 12.5 mm – installation allows direct axial location through the flange, eliminating the need for additional retaining rings or circlips, significantly simplifying installation and saving axial space.

 

✅ 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.

 

✅ This bearing is manufactured from all-stainless steel (rings, balls, and cage all stainless steel), offering excellent corrosion resistance, particularly suitable for humid, corrosive, or high-cleanliness environments.

 

✅ Ensure shaft and housing fits comply with P0 grade requirements. Shaft abutment diameter: da min. ≈ 5.7 mm, da max. ≈ 6.2 mm; housing abutment diameter: Da max. ≈ 9.9 mm; maximum chamfer radius: ra max. 0.15 mm.

 

✅ Due to the compact size (only 2 g), use specialized 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 customization, and intelligent upgrading, transforming precision bearings into core solutions addressing pain points across multiple industries. The NMT W 638/5 R-2Z bearing is manufactured to strict Japanese quality standards – from ring material (high-purity stainless steel) and rolling elements to superfinishing processes. The combination of integral flanged design (R), all-stainless steel material (W series), 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 flanged convenience, maintenance-free sealing, high corrosion resistance, and precision performance.

 

Choose NMT W 638/5 R-2Z for:

 

✅ Integral flanged design – easy installation, space saving

 

✅ Double metal shields – maintenance-free, extended life

 

✅ All-stainless steel material – high corrosion resistance, extended life

 

✅ Compact miniaturization – 5×11×5 mm, flange OD 12.5 mm, only 2 g

 

✅ 60,000 r/min high-speed performance – industry-leading

 

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

 

✅ Stainless steel stamped 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