Product Overview

The NMT 7008 ACD/P4ADT is a pre-assembled duplex tandem matched super-precision angular contact ball bearing set, comprising 2 rows of bearings precisely paired in the same direction (<<). With a total width of 30 mm (15 mm per row × 2), a 40 mm bore, and a 68 mm outer diameter, this set features a 25° contact angle (AC type) and high-capacity D-type design, specifically optimized for high-speed rotational applications dominated by heavy unidirectional axial loads.

 

The bearing set offers a basic dynamic load rating of 26.0 kN and a static load rating of 20.8 kN – nearly double the capacity of a single 7008 series bearing – effectively handling powerful thrust loads combined with radial forces. The P4A super-precision tolerance class ensures micron-level rotational accuracy even at elevated speeds.

 

Model Code Decoding – Understanding NMT 7008 ACD/P4ADT

Code Meaning

7008 Basic series designation, 40 mm bore

AC Angular contact design with 25° contact angle – balancing high axial rigidity and radial capacity

D High-capacity D-type design with increased rolling element complement

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

DT Duplex Tandem designation – 2 bearings mounted in the same direction (<<) , with end faces precision-ground at factory. Not interchangeable with individual bearings

Critical Feature: The DT tandem arrangement means both bearings share the same contact angle orientation. Axial loads are shared equally across both rows, enabling extreme unidirectional thrust capacity. This matched set does not come with a preset internal preload (marked as "not applicable"). Actual operating preload must be adjusted during installation via locknut torque or spacer selection to suit specific speed and load conditions.

 

Core Performance Advantages

1. Tandem Arrangement – Doubled Unidirectional Axial Capacity

With both rows oriented identically, axial load capacity increases by nearly 100% compared to a single bearing. The 26.0 kN dynamic and 20.8 kN static ratings make this set ideal for heavy-cutting lathe spindles, powerful drilling spindles, and other unidirectional thrust applications.

 

2. 25° Contact Angle – Powerful Combined Radial-Axial Load Capacity

The 25° angle delivers excellent axial stiffness while retaining ample radial capacity, perfectly matching the combined load demands of most machine tool spindles – radial cutting forces plus axial feed forces.

 

3. Factory Precision Matching – Uniform Load Distribution

Every DT set undergoes end-face matching grinding at the NMT factory, ensuring highly uniform load sharing between the two bearings in tandem installation, preventing individual bearing overload and significantly extending overall set service life.

 

4. P4A Super-Precision Grade – High Speed & High Accuracy Combined

The P4A tolerance class guarantees minimal running runout. Combined with the moderate heat generation of the 25° contact angle, the set maintains stable geometric accuracy and temperature performance at high speeds.

 

5. All-Steel High-Capacity Construction

Premium bearing steel with D-type large-ball design delivers robust impact resistance while maintaining a high limiting speed, well-suited for interrupted cutting and vibration-prone metal machining conditions.

 

Typical Applications

The NMT 7008 ACD/P4ADT is ideally suited for high-speed precision equipment where unidirectional axial loads dominate:

 

CNC Lathe Spindles – sustaining continuous axial cutting feed forces

 

Vertical/Horizontal Machining Centers – heavy milling spindles (fixed axial direction)

 

Deep-Hole Drilling Spindles – high-thrust drilling and gun-drilling applications

 

Grinding Machine Wheel Spindles – high-speed rotation under unidirectional grinding forces

 

High-Speed Electric Spindles – precision machining units with constant axial load direction

 

Industrial Pumps/Compressors – unidirectional thrust positioning in high-speed rotating shafts

 

Important Installation Notes

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

 

⚠️ The tandem arrangement (<<) is directional. Ensure the contact angle direction points toward the incoming axial load – incorrect orientation will eliminate load capacity.

 

⚠️ This set does not have a preset internal preload. Actual preload must be controlled during installation via locknut torque or precision spacers. Strictly follow NMT's installation guidelines and recommended torque values.

 

⚠️ Maximum limiting speed depends on lubrication, preload amount, and heat dissipation. Please consult NMT technical engineers for customized speed recommendations.

 

NMT Quality Commitment

Japan NMT (Enmutī) applies stringent end-face parallelism and height-difference matching grinding to every DT tandem set, ensuring load-sharing deviation between the two rows is minimized to an extremely small range. The 7008 ACD/P4ADT delivers P4A accuracy, D-type high-capacity design, and tandem-doubled axial capability for long-lasting, stable rotational support in your heavy-duty unidirectional-load spindles.

 

Choose NMT 7008 ACD/P4ADT for:

 

✅ Japanese precision matched assembly craftsmanship

 

✅ Tandem arrangement doubling axial load capacity

 

✅ 25° contact angle optimized for combined loads

 

✅ P4A super-precision running accuracy

 

✅ All-steel D-type high-capacity design

 

✅ Open preload adjustment for flexible application tuning