Product Overview

The NMT 7012 ACE/P4ADBB is a pre-assembled duplex back-to-back matched super-precision all-steel angular contact ball bearing set, comprising 2 rows of bearings precision-paired in a back-to-back (<>) configuration. With a total width of 36 mm (18 mm per row × 2), a 60 mm bore, and a 95 mm outer diameter, this set features a 25° contact angle (ACE type) and high-speed E-type design, combined with all-steel rolling elements and a phenolic resin cage, factory-preset with Class B light preload. It delivers ultimate system rigidity, exceptional overturning moment resistance, and bidirectional axial load capacity, accommodating radial and bidirectional axial loads simultaneously.

 

The bearing set offers a radial dynamic load rating of 5,850 lbf (26.0 kN) and a radial static load rating of 5,512 lbf (24.5 kN) . The DB back-to-back configuration extends the load action points outward, creating a maximum effective span that provides the highest overturning moment rigidity and bidirectional axial load capacity. Manufactured to the P4A super-precision tolerance class with E-type high-speed design and Class B light preload, the set achieves a limiting speed of 33,000 r/min. The operating temperature range is -30°C to 110°C.

 

Model Code Decoding – Understanding NMT 7012 ACE/P4ADBB

Code Meaning

7012 Basic series designation, 60 mm bore, 95 mm OD

ACE 25° contact angle + High-speed E-type design – 25° contact angle provides superior axial and radial load capacity; E-type offers higher speed capability and can accommodate heavier loads than equivalent B-type designs

P4A Super-precision tolerance class – dimensional accuracy to ISO P4 class (ABEC 7), bore and OD tolerances -0.004mm to 0

DB Duplex Back-to-Back – 2 bearings mounted with contact angles facing outward (<>), providing maximum overturning rigidity and bidirectional axial load capacity

B Class B light preload – optimized internal contact stiffness for high-speed precision applications

Core Value: The DB back-to-back configuration extends the load action points outward, maximizing the effective span and significantly enhancing spindle resistance to bending moments. The E-type high-speed design offers higher speed capability and can accommodate heavier loads than equivalent B-type designs. P4A super-precision ensures bore and OD tolerances are controlled within -0.004mm to 0 – these three elements work together to make this bearing set the flagship precision bearing solution offering the perfect balance of ultimate rigidity and ultra-high-speed performance.

 

Core Performance Advantages

1. Back-to-Back (DB) Configuration – Ultimate Overturning Rigidity and Bidirectional Load Capacity

The back-to-back (<> ) arrangement orients the contact angles outward in opposite directions, maximizing the effective span and providing the highest overturning moment rigidity. Whether facing axial load direction changes, radial cutting force fluctuations, or bending moment impacts, this configuration delivers the most stable rotational support. The precision-matched pair ensures uniform load distribution across both rows, significantly enhancing overall system rigidity.

 

2. 25° Contact Angle (ACE Type) + High-Speed E-Type Design – Ultra-High Speed and Heavy Load Combined

The 25° contact angle delivers superior axial rigidity while maintaining ample radial capacity. The E-type high-speed design optimizes internal geometry and rolling element parameters, significantly reducing sliding friction and churning losses at high speeds. Compared to equivalent B-type high-speed bearings, the E-type design offers higher speed capability and can accommodate heavier loads. Combined with a phenolic resin cage, the set achieves a limiting speed of 33,000 r/min.

 

3. High Load Capacity – High Load in Compact Space

With optimized rolling element parameters (ball diameter 7.938 mm, 25 balls per bearing), it achieves an outstanding 5,850 lbf (26.0 kN) dynamic and 5,512 lbf (24.5 kN) static load rating within a compact 36 mm total width. The set weighs only 0.833 – 0.84 kg.

 

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

Class B 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 33,000 r/min limiting speeds.

 

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

The P4A tolerance class (ABEC 7) guarantees minimal radial runout and axial play. Bore and outside diameter tolerances are -0.004mm to 0, meeting stringent surface quality and dimensional consistency requirements. Operating temperature range is -30°C to 110°C.

 

6. Lightweight Phenolic Resin Cage

The lightweight high-strength phenolic resin cage provides excellent guidance accuracy and low friction at high speeds, contributing to reduced centrifugal forces, friction, and heat generation – a key factor in achieving the 33,000 r/min limiting speed.

 

7. All-Steel Construction – High Rigidity, Impact Resistance, Cost-Effectiveness

Premium chrome steel rings and balls offer higher fracture toughness and impact resistance than hybrid ceramic versions – more reliable under interrupted cutting and accidental overload conditions. All-steel bearings also offer significant cost advantages for high-volume industrial applications.

 

8. Clear Performance Specifications

 

Parameter Value

Bore d 60 mm

Outer Diameter D 95 mm

Total Width B 36 mm (2×18 mm)

Contact Angle 25°

Dynamic Radial Load 5,850 lbf (26.0 kN)

Static Radial Load 5,512 lbf (24.5 kN)

Ball Diameter Dw 7.938 mm

Balls per Bearing 25

Limiting Speed 33,000 r/min

Ball Material Chrome Steel

Ring Material Chrome Steel

Cage Material Phenolic

Seal Type Open

Tolerance Class P4A (ABEC 7)

Preload Class B (Light)

Arrangement Back-to-Back (<> ) DB

Bearings in Set 2

Weight 0.833 – 0.84 kg

Temperature Range -30°C to 110°C

Typical Applications

The NMT 7012 ACE/P4ADBB, with its DB back-to-back ultimate overturning rigidity, E-type high-speed design, and P4A super-precision grade, covers an exceptionally wide range of high-end applications:

 

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

 

High-Speed Electric Spindles – high-speed rotary units

 

Machining Center Spindles – vertical/horizontal spindle systems

 

Precision Rotary Tables – high-accuracy rotary positioning

 

Aerospace Components – gyroscopes, actuators, jet engine parts

 

Medical Equipment – high-speed dental drills and medical imaging devices

 

Semiconductor Manufacturing Equipment – precision wafer processing spindles

 

Industrial Robots – high-precision transmission mechanisms and rotary axes

 

Important Installation Notes

⚠️ This is a non-universal matchable fixed set (DB)  – the 2 bearings are supplied as one complete unit. Do not interchange or mix with other bearings of the same model.

 

⚠️ The back-to-back configuration (<> ) is directional. Ensure the contact angles face outward to achieve the expected overturning rigidity.

 

✅ This set 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 -0.004mm to 0).

 

✅ This set is open design – select appropriate lubrication method based on application. To achieve the 33,000 r/min limiting speed, oil-air or oil-mist lubrication is recommended.

 

⚠️ Ensure shaft and housing bore concentricity and straightness meet P4A grade requirements to achieve the expected rotational accuracy and service life.

 

NMT Quality Commitment

Japan NMT (Enmutī) applies strict Japanese quality standards to every 7012 ACE/P4ADBB bearing set – from ring material (high-purity chrome steel) and rolling elements to superfinishing processes. Every DB back-to-back set undergoes factory end-face matching grinding and Class B light preload setting, ensuring load-sharing deviation between the two rows is minimized to an extremely small range. The combination of 25° contact angle (ACE type), E-type high-speed design, DB back-to-back ultimate rigidity, P4A precision, and Class B light preload makes this bearing set the flagship precision bearing solution in the NMT 7012 series – offering the perfect balance of ultimate overturning rigidity and ultra-high-speed performance.

 

Choose NMT 7012 ACE/P4ADBB for:

 

✅ DB back-to-back configuration – ultimate overturning rigidity and bidirectional axial load capacity

 

✅ E-type high-speed design – 33,000 r/min ultra-high speed and heavy load combined

 

✅ 25° contact angle – superior combined radial and axial load capacity

 

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

 

✅ P4A super-precision running accuracy

 

✅ All-steel – high rigidity, impact resistance, cost-effectiveness

 

✅ Factory pre-matched – ready to install