NSK7906A5TYNSULP4Super Precision Angular Contact Ball Bearing 30x47x9 mm, 25° Contact Angle, Polyamide Cage, ABEC 7 / P4, Universally Ground Light Preload

Product Description

What this part is

An NSK 7906A5 super-precision angular contact ball bearing, 30 mm bore x 47 mm outside diameter x 9 mm wide — the 71906 / 7906 thin-section spindle envelope. It carries radial load plus thrust in one direction, and the high shoulder must face the thrust. This is a machine-tool spindle bearing, not a general-purpose bearing.

Decoding the designation

7906 – single-row angular contact ball bearing, 19-series thin section, 30 x 47 x 9 mm.
A5 – NSK contact-angle code for 25°. This is the one to read carefully: in NSK nomenclature C = 15°, A5 = 25°, A = 30°, so a 7906A and a 7906A5 are not the same bearing.
TYN – moulded polyamide (nylon) cage.
SUL – single, universally ground, light preload. Single and duplex readings are mutually exclusive: this is one bearing, ground so that any two of them clamp up to a defined light preload.
P4 – ISO tolerance class 4, equivalent to ABEC 7.

What these specs mean in practice

25° is the middle of the contact-angle range: more thrust capacity and axial stiffness than a 15° bearing, more speed capability and less heat than a 40°. On a thin-section 19-series bearing like this the choice matters even more, because the small ball complement gives you less margin either way.

Universal grinding is the feature that makes the bearing useful in a spindle. The faces are ground to a controlled offset so any two bearings from this designation can be clamped face-to-face, back-to-back or in tandem and arrive at the same light preload without shimming at the bench. Light preload keeps heat and power draw down while removing axial play — the right choice for high-speed grinding and milling spindles, where a medium or heavy preload would simply generate heat. The polyamide cage runs quiet and tolerates marginal lubrication, but it is temperature-limited compared with a phenolic or machined cage, so keep it away from sustained high heat.

P4 / ABEC 7 controls bore, outside diameter, width and, critically, radial and axial runout, so the ring can be installed in any rotational orientation without hunting a high spot.

Published dimensions

Bore (d): 30 mm
Outside diameter (D): 47 mm
Width (B): 9 mm
Contact angle: 25°
Rows: 1
Cage: moulded polyamide (TYN)
Precision: ISO P4 / ABEC 7
Preload: light, universally ground (SUL)
Closure: open, no seals or shields

Quantity and configuration

Sold as one bearing. SU means single — this is not a factory-matched duplex pair, so no set preload is supplied with a partner. Because it is universally ground, however, two of these clamp up into a defined light-preload pair, which is normally how they are used. If your drawing calls for a factory duplex pair, that is the DUL designation rather than SUL.

Fitting notes

Orient the bearing so the high shoulder faces the thrust load. Press or heat onto the shaft against the inner ring only — never hammer a P4 bearing and never drive force through the cage. Clamp the rings fully; a partially clamped universally-ground bearing never develops its designed preload. Grease sparingly, roughly a quarter to a third fill, or run the oil-air system the spindle was built around. A single angular contact locates the shaft one way only and needs an opposing bearing in the arrangement.

Interchange guidance

Direct 30 x 47 x 9 mm super-precision 25° equivalents, all confirmed as 25° in their own schemes: SKF 71906 ACD/P4A (SKF AC = 25°), RHP 7906ETP4 and 7906E (RHP E = 25°), FAG B71906-E-T-P4S (FAG E = 25°), Fafnir/Timken 3MM9106WICR (3MM = 25°). Carried as dimensionally-correct cross-references with the difference named: NSK 7906CTYNSULP4 and SKF 71906 CD/P4A are the same envelope at 15°, NSK 7906A is the same envelope at 30°, and Fafnir 2MM9106WI is 15°. All fit the same bore and housing, so match the angle your spindle was designed around before substituting. NSK also absorbed RHP, so RHP 7906 numbers are part of the same lineage.