NSK7208A5TYDUMAngular Contact Ball Bearing Duplex Pair – 40 mm Bore, 80 mm OD, 18 mm Width, 25 Degree Contact Angle, Medium Preload, Open, Universally Ground

Product Description

What this part is

An NSK angular contact ball bearing, 40 mm bore, 80 mm outside diameter, 18 mm width per bearing, supplied as a duplex pair with medium preload. The 7208 designation places it in the ISO 72 medium series at the 08 bore code, so the boundary dimensions follow the ISO standard and are common across manufacturers.

Decoding the designation

In 7208-A5TY-DUM the 72 is the ISO dimension series and 08 the bore code, giving the 40 mm bore. A5 is NSK’s code for a 25° contact angle. DU marks a duplex pair and M sets medium preload. The A5 characters are read together as one code: an A on its own denotes 30° in the NSK scheme, so the pairing of A with 5 is what fixes the angle at 25°.

What these specs mean in practice

A 25° contact angle sits between the 15° high-speed setting and the 40° high-thrust setting, carrying appreciably more axial load than a 15° bearing in the same envelope and running at a lower ceiling speed. Medium preload gives more stiffness than light preload at the cost of higher running torque and more heat generated in the bearing, which suits duty where positioning accuracy under load matters more than the top of the speed range. The 7208 medium series is a heavier section than the 7008 light series at the same 40 mm bore, trading outside diameter and width for capacity.

Load ratings and speed

Dynamic load rating 34.5 kN (7,756 lbf), static load rating 24.1 kN (5,418 lbf), limiting speed 16,700 rpm on grease. Operating range −30 °C to 100 °C.

Thrust direction and arrangement

A single-row angular contact ball bearing takes thrust in one direction only, set by which ring carries the high shoulder. The two bearings assembled as a duplex pair carry thrust in both directions, and the ground offset on the ring faces establishes the medium preload. Universal grinding means any two bearings of this designation may be arranged back-to-back, face-to-face or in tandem and will develop the specified preload when clamped.

Quantity and configuration

2 Pcs, two separate bearings forming one duplex pair. The 18 mm width is per bearing, giving 36 mm across the assembled pair. Open on both faces, no snap ring groove, straight bore, no relubrication provision in the outer ring.

Fitting notes

Preload develops as the ground ring faces are clamped together, so the shaft and housing shoulders act as the datum and the clamp load must reach the faces squarely. The face marking establishes the intended orientation of the pair.

Interchange guidance

Genuine interchanges match series, angle, arrangement and preload: SKF 7208 ACD/P4ADMA uses the SKF AC code for 25° in a medium-preload pair, and FAG B7208-E-T-P4S-DUM uses the FAG E code for 25°. RHP 7208A5TYNDUMP4 is the closely related RHP designation in the same nomenclature family. Same-envelope 7208 bearings at 15° (NSK C) or 30° (NSK A) are related sizes rather than interchanges because the contact angle sets the load split, and light or heavy preload variants of the same number are likewise related rather than equivalent.