NSK7208CTYDFP4LSuper Precision Angular Contact Ball Bearing Pair 40x80x18 mm, 15° Contact Angle, Face-to-Face Matched, ABEC 7

Product Description

What this part is

A face-to-face matched pair of super-precision angular contact ball bearings in the 40 mm bore × 80 mm outside diameter × 18 mm width envelope, the ISO 7208 size. Single row each, ground and matched as a set.

Decoding the designation

In the NSK super-precision scheme C is a 15° contact angle, distinct from A at 30° and A5 at 25°, so a 7208C and a 7208A5 are different bearings sharing one envelope. DF is duplex face-to-face, a factory-matched pair. P4 is the class equivalent to ABEC 7, and the trailing L gives light preload.

What face-to-face matching does

In a face-to-face pair the two contact-angle lines converge inward toward the bearing axis, giving a short effective load span. The pair locates the shaft axially in both directions and tolerates a small amount of angular misalignment between the two seats more readily than a back-to-back pair does. A back-to-back pair, by contrast, diverges the load lines outward for a long span and higher moment rigidity. The two arrangements are not interchangeable in a spindle designed around one of them.

Thrust direction

Each bearing in the pair carries radial load together with thrust in one direction only. The pair as mounted face-to-face takes thrust in both directions, one row acting in each.

What these specs mean in practice

A 15° contact angle carries more radial load and runs faster than a 25° or 30° bearing of the same size, and carries correspondingly less thrust. Light preload favours speed and low heat generation over maximum axial rigidity, which is the usual choice at the faster end of a spindle range. The 18 mm width on a 40 mm bore places this in the 72 dimension series.

Quantity and configuration

2 Pcs. One factory-matched face-to-face pair, supplied without spacers, locknut or housing. The set is matched as a unit.

Fitting notes

The two bearings go onto the shaft with their marked faces oriented as supplied, against a square clean shoulder. The matched preload is only realised when both outer rings seat fully in the housing bore.

Interchange guidance

The same-spec equivalents are RHP 7208CTDFP4 and Timken 2MM208WI CR DF. A 7208 in the same envelope with a different contact angle or a different matching arrangement, such as a 7208A5 or a DB-matched pair, is a related size rather than a substitution.