Product Overview

The NMT S71901 ACDGB/P4A is a sealed, universally matchable single-row super-precision angular contact ball bearing. With a 12 mm bore, 24 mm outer diameter, and 6 mm width, this bearing is the ultra-compact member of the 719 series. Featuring a 25° contact angle (ACD type) and D-type high-capacity design, combined with all-steel rolling elements and a phenolic resin cage, factory-preset with Class B light preload (GB) , and equipped with non-contact rubber seals on both sides, it integrates high axial rigidity, high load capacity, maintenance-free sealing, and flexible arrangement capability into a single package, accommodating radial and unidirectional axial loads simultaneously.

 

The bearing offers a radial dynamic load rating of 2.55 kN (574 lbf) and a static load rating of 1.18 kN (266 lbf) . The GB universal matchable suffix indicates that this bearing features universal matchable (SU) capability – any two bearings of the same model can be directly paired without selective shimming or additional grinding. Users can freely configure them in back-to-back (<>), face-to-face (><), or tandem (>>) arrangements. Manufactured to the P4A super-precision tolerance class with a 25° contact angle and Class B light preload, the bearing delivers exceptional high-speed performance with enhanced system rigidity. The bearing weighs only 0.01 kg (10 g) with an operating temperature range of -30°C to 110°C.

 

Model Code Decoding – Understanding NMT S71901 ACDGB/P4A

Code Meaning

S Sealed design – equipped with non-contact rubber seals on both sides

71901 Basic series designation, 12 mm bore, 24 mm OD, 6 mm width

AC Angular contact design with 25° contact angle – provides higher axial rigidity and axial load capacity compared to 15° designs

D D-type high-capacity design – accommodates heavy loads at relatively high speeds

G Universally matchable – any two bearings of the same model can be directly paired

B Class B light preload – eliminates internal clearance, reduces deflection, improves system stiffness

P4A Super-precision tolerance class – superior to ABEC 7, running accuracy superior to P4

Core Value: The S sealed design effectively prevents contaminant ingress, extending bearing service life. GB universal matchability (SU) means every NMT S71901 ACDGB/P4A bearing's end-face height difference and parallelism are tightly controlled, allowing any two bearings of the same model to be directly paired without selection or re-grinding. The ACD-type 25° contact angle provides higher axial rigidity and axial load capacity compared to 15° designs. The D-type high-capacity design accommodates heavy loads at relatively high speeds. Class B light preload eliminates internal clearance and improves system stiffness. P4A super-precision ensures bore and OD tolerances are controlled within -0.004 mm to 0 – these six elements work together to make this bearing the ultimate precision bearing solution for miniature high-rigidity spindles.

 

Core Performance Advantages

1. Non-Contact Seals – Maintenance-Free, Extended Life

The bearing features non-contact rubber seals on both sides that effectively prevent contaminants such as cutting fluids and dust from entering the bearing interior, while the non-contact design avoids friction between the seal lip and the inner ring – adding no extra resistance or heat generation. This ensures stable temperature performance even at ultra-high speeds, while significantly extending maintenance intervals.

 

2. 25° Contact Angle – High Axial Rigidity and Load Capacity

The 25° contact angle is one of the highest axial rigidity contact angle designs available in angular contact ball bearings. Compared to 15° contact angle designs, the ACD-type 25° contact angle provides higher axial rigidity and greater axial load capacity. In applications subjected to heavy axial loads, the 25° contact angle more effectively resists axial displacement, ensuring machining accuracy and spindle stability.

 

3. D-Type High-Capacity Design – High Load in Compact Space

The D-type high-capacity design optimizes ball complement and internal geometry – ball diameter 3.175 mm, 13 balls per bearing – achieving an outstanding 2.55 kN (574 lbf) dynamic and 1.18 kN (266 lbf) static load rating. Within an extremely compact 6 mm width, it provides load capacity far exceeding bearings of the same size class.

 

4. Universal Matchable (GB) – One Inventory, Infinite Arrangements

GB universal matchability delivers outstanding value:

 

Simplified inventory: Stock a single model to cover DB (<>), DF (><), and DT (>>) pairing needs

 

On-site flexibility: Change arrangements during commissioning based on actual load directions

 

Easy maintenance: Replace individual bearings without replacing entire matched sets

 

No shims required: Install directly to achieve design preload

 

5. Class B Light Preload – Ideal for High-Speed Precision Applications

Class B light preload provides precise internal contact stiffness for high-speed spindles – eliminating internal clearance, reducing vibration and noise at high speeds, while avoiding excessive temperature rise from over-preloading, and enhancing system stiffness. Compared to Class A extra light preload (GA), Class B preload provides higher system rigidity, making it particularly suitable for applications with greater stiffness requirements. This ensures stable performance even at the limiting speed.

 

6. P4A Super-Precision Grade – Micron-Level Accuracy

The P4A tolerance class (superior to ABEC 7) guarantees minimal radial runout and vibration. Bore and outside diameter tolerances are -0.004 mm to 0. Distance to pressure point a = 7.3 mm.

 

7. Extreme Lightweight – Only 10 Grams

The bearing weighs only 0.01 kg (10 g) . The extremely low rotating mass effectively reduces centrifugal loads and inertia moments at high speeds.

 

8. Lightweight Phenolic Resin Cage

The lightweight high-strength phenolic resin cage provides excellent guidance accuracy and low friction at high speeds. This material offers an excellent strength-to-weight ratio, contributing to reduced centrifugal forces, friction, and heat generation.

 

9. Factory Pre-Lubricated – Ready to Install

This bearing comes pre-lubricated from the factory with high-performance grease – ready to install out of the box without additional lubrication handling, significantly simplifying the assembly process.

 

10. Clear Performance Specifications

 

Parameter Value

Bore d 12 mm

Bore Tolerance -0.004 mm to 0

Outer Diameter D 24 mm

OD Tolerance -0.004 mm to 0

Width B 6 mm

Contact Angle 25°

Dynamic Radial Load 2.55 kN (574 lbf)

Static Radial Load 1.18 kN (266 lbf)

Ball Diameter Dw 3.175 mm

Balls per Bearing 13

Distance to Pressure Point a 7.3 mm

Ball Material Chrome Steel

Ring Material Chrome Steel

Cage Material Phenolic Resin

Seal Type Non-Contact Rubber Seals (both sides)

Tolerance Class P4A

Preload Class B (Light)

Arrangement Universal Matchable (SU)

Weight 0.01 kg (10 g)

Temperature Range -30°C to 110°C

Typical Applications

The NMT S71901 ACDGB/P4A, with its sealed protection, 25° contact angle high axial rigidity, and universal matchable flexibility, covers an exceptionally wide range of high-end miniature applications:

 

Machine Tool Spindles – CNC machine tools, precision grinders, machining center spindles

 

High-Speed Machinery – PCB drilling machines, engraving machines

 

Aerospace Components – gyroscopes, precision actuators

 

Medical Equipment – high-speed dental handpieces, surgical tools, medical imaging devices

 

Semiconductor Manufacturing – precision wafer processing spindles

 

High-Frequency Motors – high-speed, high-precision miniature motors

 

Industrial Robots – micro high-speed rotary joints

 

Precision Instruments – measuring devices, optical scanners

 

Optical Scanning Devices – high-speed rotating mirrors, laser scanning

 

Indexing Heads and Rotary Tables – high-accuracy rotary positioning

 

Important Installation Notes

✅ This bearing is universally matchable (GB) – any two bearings of the same model can be directly paired. Configurable as back-to-back (<>), face-to-face (><), or tandem (>>) arrangements.

 

✅ This bearing features non-contact seals and comes pre-lubricated from the factory with grease – ready to install out of the box.

 

✅ For paired installations, using bearings from the same production batch is recommended for optimal consistency.

 

⚠️ This bearing comes with factory-preset Class B light preload. No additional preload adjustment is required during installation. However, ensure shaft and housing fits comply with P4A grade requirements (bore/OD tolerance -0.004 mm to 0).

 

⚠️ A single-row angular contact ball bearing can accommodate axial load in one direction only. Paired installations (DB/DF/DT) are required for bidirectional axial load capacity.

 

⚠️ Ensure the contact angle direction matches the intended load direction – incorrect orientation will eliminate load capacity.

 

⚠️ Due to the extremely small size (only 10 g), extra care is required during installation to avoid excessive force.

 

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

 

⚠️ GB suffix indicates Class B light preload, which differs from GA (Class A extra light preload). Class B provides higher system stiffness – select the appropriate preload class based on application requirements.

 

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 S71901 ACDGB/P4A bearing is manufactured to strict Japanese quality standards – from ring material (high-purity chrome steel) and rolling elements to superfinishing processes. End-face height difference, parallelism, and contact angle deviation of each bearing are tightly controlled to ensure universal matchability consistency across any two bearings of the same model. The combination of non-contact seals (S), 25° contact angle (ACD type), D-type high-capacity design, P4A precision, Class B light preload, and universal matchable flexibility makes this bearing the flagship miniature precision bearing in the NMT 719 series – offering the perfect balance of high axial rigidity, maintenance-free operation, and flexible arrangement.

 

Choose NMT S71901 ACDGB/P4A for:

 

✅ Non-contact seals – maintenance-free, extended life

 

✅ 25° contact angle – high axial rigidity and load capacity

 

✅ D-type high-capacity design – 2.55 kN (574 lbf) high load capacity

 

✅ Universal matchable – one inventory, infinite arrangements

 

✅ Class B light preload – ideal for high-speed precision applications, higher system stiffness

 

✅ P4A super-precision running accuracy – bore/OD tolerance -0.004 mm to 0

 

✅ Extreme lightweight – only 10 g

 

✅ Phenolic resin cage – low friction, low noise, high speed

 

✅ Factory pre-lubricated – ready to install