NSKPrecision Angular Contact Ball Bearing Matched Back-to-Back Pair (2 Pcs), 17 x 47 x 14 mm, 30 Degree Contact Angle, ABEC-5 P5, Phenolic Cage

Product Description

What this part is

A matched back-to-back pair of NSK precision angular contact ball bearings, 17 mm bore, 47 mm outside diameter, 14 mm wide each. Both carry a 30° contact angle, are ground to ISO Class 5 (ABEC 5), and run a phenolic resin cage, the deep red-brown cage visible in the photographs. The 73 dimension series is the heavy one for this bore: a 17 mm shaft in a 47 mm housing gives more thrust capacity than the 70- or 79-series bearings on the same bore, at the cost of speed.

Designation breakdown

Decoded against NSK’s own numbering system. Suffix letters are brand-specific and this reading applies to NSK numbers.

7303: single-row angular contact ball bearing, 03 dimension series, bore number 03 = 17 mm bore, 47 mm outside diameter, 14 mm width. A: 30° contact angle in NSK’s scheme, which runs C = 15°, A5 = 25°, A = 30°. SKF’s AC is 25°. T: phenolic resin cage. NSK documents T and TR as its phenolic cage options, TR being the outer-ring-guided version. The photographs confirm phenolic, since the reddish-brown cage is the visual marker. DB: back-to-back duplex arrangement, the O configuration. DF is face-to-face and DT is tandem. P5: ISO tolerance class 5, equivalent to ABEC 5. +KL-22A: a supplementary code printed on the carton, recorded as it appears. It does not change bore, outside diameter, width, angle or class.

The carton is also marked RM-55, and the rings are stamped 7303A / 7303 / NSK / JAPAN with a hand-written set marking.

Arrangement and contact angle

In a back-to-back pair the two contact-angle lines diverge outward, so the effective load centres sit well outside the bearing faces. A DB set is stiff against moment (tilting) loads and takes thrust in both directions from a single bearing station. Face-to-face converges the load lines and tolerates misalignment better, with less moment stiffness. Tandem points both angles the same way to double one-direction thrust and carries nothing in reverse.

A 30° angle is the high-thrust end of the range. It carries and resists more axial load than a 15° bearing and is axially stiffer, and it gives up speed and some radial rigidity in exchange. For high rpm with light thrust, a 15° C-suffix bearing is the corresponding part.

The phenolic cage is light, has low inertia at speed and holds oil in its pores, which helps through marginal lubrication. NSK rates its phenolic cages to 120°C, below the sustained temperature a machined brass cage handles.

Published ratings and mounting data

NSK publishes these figures for the 7303A envelope. Single-bearing values. Bore (d): 17 mm. Outside diameter (D): 47 mm. Width (B): 14 mm per bearing. Contact angle: 30°. Basic dynamic load rating (Cr): 17,500 N per bearing. Basic static load rating (C0r): 8,650 N per bearing. Limiting speed, single bearing: 11,000 rpm grease, 15,000 rpm oil-bath. Effective load centre (a): 16.2 mm. Shaft abutment diameter (da min.): 23 mm. Housing abutment (Da max.): 41 mm. Chamfers: r min. 1.0 mm, r1 min. 0.6 mm. Fillet ra max.: 1.0 mm. Mass: approximately 0.116 kg per bearing.

Matched back-to-back set values. Overall mounted width (2B): 28 mm. Basic dynamic load rating (Cr), pair: 28,500 N. Basic static load rating (C0r), pair: 17,300 N. Limiting speed, pair: 9,000 rpm grease, 12,000 rpm oil-bath. Load centre spacing (a0): 32.5 mm. Housing abutment Db max.: 42 mm. Fillet rb max.: 0.6 mm. Mass: approximately 0.232 kg for the pair. Tolerance class: P5 (ISO Class 5 / ABEC 5). Cage: phenolic resin. Closure: open, no seals and no shields. Rows: one per bearing.

A DB pair’s rated speed is lower than a single bearing’s, because two preloaded bearings in one station generate more heat than one.

Set composition

What ships is two bearings, one matched DB pair, in the original NSK carton. The photographs show exactly two bearings, bagged together, ring-marked as a set.

A matched pair is ground so the ring faces reach the designed preload when clamped solid, with no shims, ground spacers or adjustment. Two unrelated singles of the same designation do not reproduce that. The two bearings stay together in their marked orientation.

Mounting data

A DB pair assembles one way round. Each outer ring has a thick land on one face and a thin land on the other. For back-to-back the thin (marked) faces go outward, so the two bearings meet on their thick outer-ring faces. Shaft abutment diameter da min. is 23 mm, housing abutment Da max. 41 mm and Db max. 42 mm. Chamfers are r min. 1.0 mm and r1 min. 0.6 mm, with fillets ra max. 1.0 mm and rb max. 0.6 mm. Overall mounted width is 28 mm. Class 5 running accuracy follows the shaft and housing accuracy, and an ABEC-5 bearing delivers the runout of the housing it sits in.

Interchange guidance

Same-envelope 17 x 47 x 14 mm alternatives include FAG 7303-B-XL-TVP and 7303-B-XL-JP (standard tolerance, 40° B angle), SKF 7303 BECBP, NTN 7303ADB, Nachi 7303ADB and NSK’s own 7303AW / 7303AWDB pressed-steel-cage versions. NSK 7303A5DB is the 25° version and NSK 7303B is 40°. Contact angle, arrangement, tolerance class and preload each govern the substitution. RHP precision bearings were absorbed into NSK, so an RHP reference in an older machine manual can legitimately point here.