SNR71906HDUJ74Super Precision Angular Contact Ball Bearing 30x47x9 mm, 25 Degree Contact Angle, Stratified Phenolic Cage, Universal Duplex Pair Light Preload, ISO Class 4

Product Description

What this part is

SNR Machline 71906HDUJ74 super-precision angular contact ball bearings in the thin-section 19-dimension series, supplied as a universal duplex pair. Brand: SNR (NTN-SNR). Bore: 30 mm. Outside Diameter: 47 mm. Width: 9 mm per bearing. Total Width: 18 mm for the assembled pair. Contact Angle: 25°. Preload: Light, 14 lbf. Precision Class: ISO 4, P4, ABEC 7. Running Accuracy: ISO 4 radial and axial runout. Cage Material: stratified cotton-fabric-reinforced phenolic. Cage Type: machined, centred on and guided by the outer ring. Bearing Material: 52100 vacuum-degassed steel rings and balls. Rolling Elements: steel balls. Closure Type: open. Bore Type: straight. Number Of Rows: 1 per bearing. Internal Clearance: N/A, the set is preloaded rather than clearance-set. Series: 719. Base Number: 71906. At 9 mm wide in a 47 mm outside diameter it is a thin-section bearing, chosen where radial space is tight and speed is the priority.

Decoding the designation

71906: ISO 19-dimension series angular contact envelope, 30 x 47 x 9 mm. H: 25° contact angle in SNR’s scheme. DU: a pair of universal bearings, selected so that bore and outside-diameter variation across the set stays within half the ISO tolerance. J74: the 7 is the preload grade, light; the 4 is the precision class, ISO 4 / P4 / ABEC 7. Searchable forms: 71906HDUJ74, 71906 H DU J74, 71906-H-DU-J74, 71906.H.DU.J74.

Load ratings and speed

Dynamic Load Rating: 8.00 kN, 1,800 lbf, per single bearing. Static Load Rating: 5.92 kN, 1,330 lbf, per single bearing. Limiting Speed: 27,000 rpm on grease and 42,000 rpm on oil, both figures for a single bearing. Lubricant: grease or oil. Speed changes when bearings are matched into an arrangement: a back-to-back pair at light preload runs at 0.80 of the single-bearing figure, giving 21,600 rpm on grease and 33,600 rpm on oil, and a face-to-face pair at light preload runs at 0.75, giving 20,250 rpm on grease and 31,500 rpm on oil. Operating Temperature Range: -30 to 120°C. Item Weight: 0.10 lb per bearing.

What these specs mean in practice

25° gives markedly more thrust capacity and axial stiffness than a 15° bearing, without the speed and heat penalty of a 30° or 40° bearing, a useful combination in a thin-section bearing where ring stiffness is already limited. On this same 30 x 47 x 9 mm envelope the 15° build is rated 1,890 lbf dynamic and turns 29,000 rpm on grease, against this bearing’s 1,800 lbf and 27,000 rpm. Light preload keeps friction and heat generation to a minimum and preserves speed capability. Stratified cotton-fabric-reinforced phenolic is light, quiet and tolerant of marginal lubrication, and centring the cage on the outer ring keeps it stable at speed. Rings and balls are 52100 vacuum-degassed steel, a high-carbon chrome bearing steel. ISO 4 gives closer runout and lower running vibration than standard tolerance, and most SNR ISO 4 bearings achieve ISO 2 run-out accuracy.

Quantity and configuration

Unit Quantity: 2 bearings, one universal duplex pair. Universal grinding leaves the inner and outer ring faces flush once preloaded, so any two bearings of this designation come up to the specified light preload when clamped, in any arrangement and with no shims. The pair mounts back-to-back for moment stiffness and two-direction thrust, face-to-face for tolerance of misalignment, or in tandem to double thrust capacity in one direction.

Interchange guidance

Equivalent designations on the same 30 x 47 x 9 mm envelope at 25° and light preload: 7906-E-T-DUL-P4 in world-number format, FAG / Schaeffler B71906-E-T-P4S-DUL, SKF 71906 ACD/P4ADGA, and the Timken Fafnir 3MM9306WI family, in which the 9300 prefix maps to the ISO 719 series and 3MM marks the 25° angle. SKF DGA and FAG DUL are both the light preload grade. A 71906C at 15° shares this envelope and is a related size rather than a substitute.