Product Overview

The NMT 7006 CD/P4ADBD 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 26 mm (13 mm per row × 2), a 30 mm bore, and a 55 mm outer diameter, this set features a 15° contact angle (CD type) , D-type high-capacity design, all-steel rolling elements, and factory-preset heavy preload (Class D) , delivering ultimate system rigidity and maximum overturning moment resistance for high-speed spindles.

 

The bearing set offers a basic dynamic load rating of 23.4 kN and static load rating of 16.0 kN – identical to the hybrid ceramic version. The back-to-back configuration provides maximum overturning moment rigidity and bidirectional axial load capability, while Class D heavy preload pushes system rigidity to its absolute limit, making it ideal for heavy-cutting, high-feed-rate, and high-impact/vibration applications. The P4A super-precision tolerance class ensures micron-level rotational accuracy even under heavy-load high-speed conditions.

 

Model Code Decoding – Understanding NMT 7006 CD/P4ADBD

Code Meaning

7006 Basic series designation, 30 mm bore, compact design

CD 15° contact angle design – higher limiting speed, lower heat generation for high-speed operation

P4A Super-precision tolerance class – dimensional accuracy P4, running accuracy exceeding P4

DB Duplex Back-to-Back – contact angle directions face outward (<>), providing maximum overturning rigidity and bidirectional load capacity

D Heavy preload (Class D) – the highest preload level, delivering ultimate system rigidity

Note: Absence of "HC" suffix indicates all-steel rolling elements (not ceramic), offering superior cost-effectiveness and impact toughness while maintaining high rigidity.

 

Core Feature: The back-to-back (<> ) configuration extends the load action points outward, creating the maximum effective span (bearing center distance) that significantly enhances spindle resistance to bending moments. Class D heavy preload ensures the highest internal contact stiffness during heavy cutting, effectively resisting elastic displacement caused by cutting forces.

 

Core Performance Advantages

1. Back-to-Back Configuration – Maximum System 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. With 23.4 kN dynamic and 16.0 kN static ratings, load capacity nearly doubles compared to single-row bearings.

 

2. Class D Heavy Preload – Ultimate Rigidity for Heavy Cutting

Class D represents the highest preload level in angular contact bearings, providing maximized internal contact stiffness. Under heavy cutting, interrupted cutting, high feed rates, and other severe conditions, Class D preload effectively suppresses elastic deflection of the spindle under cutting forces, significantly enhancing machining accuracy and surface quality. For applications pursuing maximum metal removal rates, Class D preload is an indispensable choice.

 

3. 15° Contact Angle – Superior High-Speed Performance

The 15° small contact angle generates less frictional heat at equivalent speeds. Even with Class D heavy preload, it maintains acceptable temperature rise levels, making it suitable for high-speed heavy-load combined conditions.

 

4. All-Steel Rolling Elements – High Rigidity and Impact Toughness

Compared to hybrid ceramic versions, all-steel construction offers higher fracture toughness and impact resistance, making it less susceptible to brittle damage under severe impact loads. For heavy cutting, interrupted machining, and other impact-prone conditions, all-steel bearings provide superior reliability and resistance to accidental overload. Additionally, all-steel bearings offer significant cost advantages – a mature choice for high-volume industrial applications.

 

5. Factory Precision Matching – Uniform Load Distribution

This is a non-universal matchable fixed set. Both bearings undergo end-face matching grinding and Class D heavy preload setting at the NMT factory, ensuring highly uniform load distribution between the two rows, preventing individual bearing overload, and significantly extending overall set service life.

 

6. Clear Performance Positioning

This set forms a clear complementary performance pair with the 7006 CD/HCP4ADBC (hybrid ceramic + Class C medium preload):

 

HCP4ADBC (hybrid ceramic + medium preload) : optimized for ultra-high speed, low heat generation

 

P4ADBD (all-steel + heavy preload) : optimized for heavy load, high rigidity, impact resistance

Users can precisely select based on primary and secondary application requirements.

 

Typical Applications

The NMT 7006 CD/P4ADBD is ideally suited for precision equipment demanding ultimate system rigidity, heavy-cutting capability, and bidirectional axial load capacity:

 

Heavy-Duty Machining Center Spindles – powerful milling and heavy boring spindles

 

Heavy-Cutting CNC Lathes – large-depth, high-feed turning spindles

 

Large Mold Engraving/Milling Machines – roughing and semi-finishing stages

 

Gear Cutting Machines – hobbing, shaping, and gear milling spindles

 

Forging/Casting Part Machining Equipment – interrupted cutting, high-impact conditions

 

Heavy Grinding Machine Wheel Spindles – large-allowance grinding

 

Important Installation Notes

⚠️ This is a non-universal matched 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 D heavy preload. No additional preload adjustment is required during installation. Critical: Shaft and housing fits must strictly comply with NMT recommended tolerances – incorrect fits can cause abnormal preload (too tight leads to overheating, too loose leads to insufficient rigidity).

 

⚠️ Class D heavy preload generates significant operating temperature rise. Oil-air lubrication is strongly recommended for adequate heat dissipation, and thermal expansion compensation should be properly预留d.

 

⚠️ Maximum limiting speed depends on lubrication, mounting fit, and heat dissipation conditions. Class D heavy preload typically results in lower limiting speeds than light/medium preload versions. Please consult NMT technical engineers for application-specific speed recommendations.

 

NMT Quality Commitment

Japan NMT (Enmutī) applies stringent end-face matching grinding and Class D heavy preload control to every DB back-to-back bearing set, ensuring load-sharing deviation between the two rows is minimized to an extremely small range. The 7006 CD/P4ADBD delivers P4A accuracy, D-type high-capacity design, 15° contact angle high-speed performance, and Class D heavy-preload ultimate rigidity for solid, long-lasting rotational support in your heavy-load heavy-cutting high-speed spindles.

 

Choose NMT 7006 CD/P4ADBD for:

 

✅ Back-to-back configuration – maximum overturning rigidity

 

✅ Class D heavy preload – ultimate system rigidity

 

✅ 15° contact angle – high speed and heavy load combined

 

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

 

✅ P4A super-precision running accuracy

 

✅ Factory pre-matched – ready to install

 

✅ Bidirectional axial load capacity

 

✅ Reliable choice for heavy-cutting conditions