1 Complete Model, Dimensions, Loads & Technical Parameters

Full Model: 7008 ACD/P4ADT

Model Code Explanation

7008: Standard boundary dimension of 70 series precision angular contact ball bearing;

ACD: 25° contact angle, high-load D internal raceway profile;

P4A: P4A ultra-precision tolerance class;

DT: Factory pre-matched tandem bearing set, arrangement <<.

Standard Dimension Parameters

Bore d: 40 mm

Outer diameter D: 68 mm

Overall width B: 30 mm

Contact angle: 25 °

Performance Data

Basic dynamic load rating Cr: 26 kN

Basic static load rating C0r: 20.8 kN

Speed note: Contact SKF for data on achievable rotational speed.

Full Product Attributes

Contact form: standard two-point contact

Number of bearing rows: 2 (complete tandem set)

Ring structure: integrated inner ring and outer ring

Internal design: high-load D optimized design

Compatible re-matching: Not available; factory pre-set set, disassembly prohibited

Duplex layout: << (tandem)

Quantity of bearings in set: 2

Preload specification: Not applicable

Tolerance class: P4A precision grade

Material: bearing steel

Coating: uncoated

Seal: open type without seals

Pre-filled lubricant: none, lubrication configured on site

Indicative carbon footprint for new product: 1.4 kg CO₂e

Net weight: 0.376 kg

eClass code: 23-05-08-04

UNSPSC code: 31171531

Note: The 25° contact angle provides superior axial load capacity. D-type raceway optimizes contact stress distribution. Bearing steel ensures stable hardness and wear resistance. Supplied as factory screened tandem set arranged <<. Tandem configuration is designed for heavy unidirectional axial loads and not suitable for bidirectional axial force. Do not split the set, otherwise matching accuracy will be lost. Open design requires external dust sealing.

2 Structure & Operating Characteristics

Japan NMT 7008 ACD/P4ADT is a 7008 size 25° high-load D-type pre-matched tandem angular contact bearing set constructed with heat-treated bearing steel rings and super-finished raceways. The 25° contact angle delivers excellent axial capacity for shafts enduring continuous unidirectional axial thrust while supporting radial loads.

Open non-sealed construction eliminates seal drag, compatible with oil-air lubrication and high-speed grease systems. No lubricant pre-filled; lubricant shall be added during assembly.

The tandem set is dimensionally selected and calibrated in factory, fixed in << arrangement to boost allowable unidirectional axial load. Consistent factory pairing reduces customers’ selection workload. Disassembly of the matched set voids matching precision. Attention: tandem arrangement cannot withstand reverse axial loads.

3 Core Performance Advantages

1. 25° contact angle + high-load D raceway: Outstanding axial bearing capacity, uniform contact stress, ideal for applications with dominant axial loads.

2. P4A ultra-precision grade: Strict rotary runout control for stable long-term accuracy.

3. Bearing steel material: High mechanical strength and excellent wear resistance for reliable continuous operation.

4. Factory pre-matched tandem << set: Fast assembly and enhanced unidirectional axial load capacity.

5. Open seal-free construction, low friction, compatible with various high-speed precision lubrication systems.

4 Typical Application Scenarios

4.1 CNC lathe spindles, deep-hole machining spindles: Rotating spindles subjected to sustained unidirectional cutting axial thrust.

4.2 Extrusion equipment, high-speed winding rotary shafts: Medium-speed operation with constant unidirectional axial load.

4.3 Special grinding machines, precision unidirectional drive units: Fixed load direction and requirements for consistent assembly quality.

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

P4A high-precision matched set must be assembled in dust-free clean workshops. Remove all burrs and metal debris on shaft and housing mating surfaces. Controlled thermal mounting is recommended for the whole unit. Never strike bearing rings or rolling elements directly. Disassembly of the matched tandem set is forbidden.

5.2 Matching & Preload Instructions

This is a factory pre-calibrated tandem bearing set fixed in << layout; free rearrangement is not allowed. No standard factory preload for tandem configuration. If preload is required by equipment design, dedicated spacers must be designed separately. Disassembly will permanently destroy original matching accuracy.

5.3 Lubrication Matching Solutions

No pre-filled lubricant. Oil-air lubrication is preferred for continuous long-duration high-speed running; dedicated high-speed grease can be used for intermittent operation. Do not mix lubricants of different brands or types. Inspect lubrication pipelines regularly.

5.4 Speed Parameter Note

Obtain limiting speed reference data from SKF. Maintain adequate safety margin according to actual load; moderately reduce operating speed under increased load to control bearing temperature.

6 Daily Maintenance & Fault Troubleshooting

Implement multi-stage low-speed progressive running-in after assembly. Raise speed to rated value only after temperature rise and vibration stabilize. Open bearings have no dustproof capability; main machine must be fitted with labyrinth or contact dust seals.

Ensure continuous and stable lubricant supply to avoid rolling surface damage caused by dry friction. In case of abnormal temperature rise, increased vibration or operating noise, sequentially check lubrication supply, mounting coaxiality, installation tolerance, load direction and actual operating load.