Product Overview

The NMT 71901 ACDGA/P4A is an open, 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 (AC type) and D-type high-capacity design, combined with all-steel rolling elements and a phenolic resin cage, factory-preset with Class A extra light preload (GA) . It integrates high axial rigidity, high load capacity, ultra-high-speed performance, super-precision rotational accuracy, 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 with a 25° contact angle and Class A extra light preload, the bearing achieves a limiting speed of 140,000 r/min. 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 71901 ACDGA/P4A

Code Meaning

71901 Basic series designation, 12 mm bore, 24 mm OD, 6 mm width – 719 series ultra-thin design

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 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 – light preload for face-to-face or back-to-back arrangements

P4A Super-precision tolerance class – superior to ABEC 7, bore and OD tolerances -0.004 mm to 0

Core Value: GA universal matchability (SU) means every NMT 71901 ACDGA/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 selective shimming or additional grinding, providing effective load sharing within a predetermined preload range. 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. 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 five elements work together to make this bearing the flagship precision bearing solution for miniature high-rigidity spindles.

 

Core Performance Advantages

1. 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.

 

2. 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.

 

3. 140,000 r/min Ultra-High Speed – Industry-Leading Performance

This bearing achieves a limiting speed of 140,000 r/min. This speed level makes it the ideal choice for ultra-high-speed miniature spindles in PCB drilling machines, dental handpieces, and high-speed engraving machines. The synergy between the 25° contact angle and Class A extra light preload ensures stable operation and low heat generation at extreme speeds.

 

4. 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

 

5. 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 140,000 r/min 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 – a key factor in achieving the 140,000 r/min limiting speed.

 

9. Open Design – Flexible Lubrication Options

This bearing features an open design, allowing flexible selection of lubrication methods based on application – grease lubrication for general ultra-high-speed applications, oil-air lubrication for extreme ultra-high-speed machining.

 

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

Limiting Speed 140,000 r/min

Ball Material Chrome Steel

Ring Material Chrome Steel

Cage Material Phenolic Resin

Seal Type Open

Tolerance Class P4A

Preload Class A (Extra Light)

Arrangement Universal Matchable (SU)

Weight 0.01 kg (10 g)

Temperature Range -30°C to 110°C

Typical Applications

The NMT 71901 ACDGA/P4A, with its 25° contact angle high axial rigidity, D-type high-capacity design, and universal matchable flexibility, covers an exceptionally wide range of high-end miniature applications:

 

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 an open design – select appropriate lubrication method based on application. To achieve the 140,000 r/min limiting speed, oil-air or oil-mist lubrication is recommended.

 

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

 

⚠️ 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 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 71901 ACDGA/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 25° contact angle (AC type), D-type high-capacity design, 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, high load capacity, and flexible arrangement.

 

Choose NMT 71901 ACDGA/P4A for:

 

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

 

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

 

✅ 140,000 r/min ultra-high-speed performance

 

✅ 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 10 g

 

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

 

✅ Open design – flexible lubrication options