Product Overview

The NMT S71901 ACDGA/HCP4A is a sealed, universally matchable single-row super-precision hybrid ceramic 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 (AC type) and D-type high-capacity design, combined with silicon nitride (Si₃N₄) hybrid ceramic rolling elements (HC) and a phenolic resin cage, factory-preset with Class A extra light preload (GA), and equipped with non-contact rubber seals on both sides, it integrates high axial rigidity, high load capacity, ultra-high-speed performance, 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). Manufactured to the P4A super-precision tolerance class (superior to ABEC 7) with a 25° contact angle and Class A extra light preload, the bearing achieves a limiting speed of 67,000 r/min under grease lubrication and 100,000 r/min under oil lubrication. The bearing weighs only 0.009 – 0.01 kg (9 – 10 g) with an operating temperature range of -30°C to 110°C.

 

Model Code Decoding – Understanding NMT S71901 ACDGA/HCP4A

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 – optimized ball complement (13 ceramic balls) and internal geometry for heavy loads at relatively high speeds

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

A Class A extra light preload – ideal for high-speed precision applications

HC Hybrid ceramic – rolling elements made of bearing-grade silicon nitride (Si₃N₄)

P4A Super-precision tolerance class – superior to ABEC 7 standards

Core Value: The S sealed design effectively prevents contaminant ingress, extending bearing service life. GA universal matchability (SU) means every NMT S71901 ACDGA/HCP4A 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 AC-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. HC hybrid ceramic technology drastically reduces centrifugal forces and frictional heat at high speeds. Class A extra light preload eliminates internal clearance and reduces vibration and noise at high speeds. P4A super-precision ensures bore and OD tolerances are controlled within -0.004 mm to 0 – these seven 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. Integral sealing prolongs bearing service life. This ensures stable temperature performance even at 100,000 r/min 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 AC-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 ceramic 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. Hybrid Ceramic Technology – The Foundation of Ultra-High-Speed Performance

Silicon nitride (Si₃N₄) ceramic balls have only 60% the density of bearing steel, drastically reducing centrifugal forces and frictional heat at high speeds. Ceramic materials also offer lower thermal expansion coefficients and higher elastic modulus, effectively suppressing geometric deformation at high speeds while providing excellent electrical insulation and extended service life. Combined with chrome steel rings and a phenolic resin cage, this achieves the perfect balance of high rigidity, ultra-high speed, and durability. The bearing achieves a limiting speed of 100,000 r/min under oil lubrication.

 

5. Universal Matchable (GA) – One Inventory, Infinite Arrangements

GA 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

 

6. Class A Extra Light Preload – Ideal for High-Speed Precision Applications

Class A extra light preload provides "just-right" 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. This ensures stable temperature performance even at the 100,000 r/min limiting speed.

 

7. 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.

 

8. Extreme Lightweight – Only 9 – 10 Grams

The bearing weighs only 0.009 – 0.01 kg (9 – 10 g). The extremely low rotating mass effectively reduces centrifugal loads and inertia moments at high speeds.

 

9. 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 – a key factor in achieving the 100,000 r/min oil lubrication limiting speed.

 

10. Factory Pre-Lubricated – Ready to Install

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

 

11. 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

Ceramic Balls per Bearing 13

Speed (Grease) 67,000 r/min

Speed (Oil) 100,000 r/min

Ball Material Silicon Nitride (Si₃N₄)

Ring Material Chrome Steel

Cage Material Phenolic Resin

Seal Type Non-Contact Rubber Seals (both sides)

Tolerance Class P4A

Preload Class A (Extra Light)

Arrangement Universal Matchable (SU)

Weight 0.009 – 0.01 kg (9 – 10 g)

Temperature Range -30°C to 110°C

Typical Applications

The NMT S71901 ACDGA/HCP4A, with its sealed protection, 25° contact angle high axial rigidity, hybrid ceramic ultra-high-speed performance, and universal matchable flexibility, covers an exceptionally wide range of high-end miniature applications:

 

High-Speed Machine Tool Spindles – CNC machine tools, precision grinders

 

High-Speed Machinery – PCB drilling machines, engraving machines

 

Aerospace Components – gyroscopes, actuators, jet engine parts

 

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

 

Important Installation Notes

✅ This bearing is universally matchable (GA) – 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.

 

✅ To achieve the 100,000 r/min oil lubrication limiting speed, oil-air or oil-mist lubrication is recommended; grease lubrication limits speed to 67,000 r/min.

 

⚠️ This bearing comes with factory-preset Class A extra 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 9 – 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 ultra-high-speed performance.

 

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 ACDGA/HCP4A bearing is manufactured to strict Japanese quality standards – from ring material (high-purity chrome steel), ceramic balls (HIP silicon nitride), 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 (AC type), D-type high-capacity design, hybrid ceramic technology (HC), P4A precision, Class A extra 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 ACDGA/HCP4A 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

 

✅ Hybrid ceramic technology – 100,000 r/min oil lubrication limiting speed

 

✅ Universal matchable – one inventory, infinite arrangements

 

✅ Class A extra light preload – ideal for high-speed precision applications

 

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

 

✅ Extreme lightweight – only 9 – 10 g

 

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

 

✅ Factory pre-lubricated – ready to install