SKF71904CDP4ADGAAngular Contact Ball Bearing — Super-Precision P4A Matched Pair, 20 mm ID, 37 mm OD, 9 mm Width, 15° Contact Angle, Extra Light Preload 25 N

Product Description

What this part is

SKF 71904 CD/P4ADGA is a matched set of two super-precision, high-capacity D design, single row angular contact ball bearings supplied at extra light preload. Bore Diameter: 20 mm. Outside Diameter: 37 mm. Overall Width: 9 mm per bearing. Total Width: 18 mm across the matched pair. Contact Angle: 15°. Preload: Extra light, 25 N. Precision Class: ABEC 7 / P4A. Rolling Elements: Ball. Number Of Rows: 1 per bearing. Bore Type: Straight. Seal Type: Open. Bearing Material: Bearing steel. Unit Quantity: 2 Pcs.

Decoding the designation

71904 — ISO 719 extra-light dimension series, bore code 04, giving a 20 x 37 x 9 mm envelope per bearing.

CD — high-capacity D design ground to a 15° contact angle, built for heavier loads than the SKF B and E high-speed designs on the same envelope.

P4A — SKF super-precision tolerance class P4A, ABEC 7 running accuracy.

DGA — universally matchable set of two bearings, extra light preload, 25 N.

What these specs mean in practice

Preload: Extra light, 25 N. Extra light preload keeps heat generation and friction low, which suits high spindle speeds, while removing internal clearance so the spindle runs without play. Axial stiffness: 22 N/µm in a back-to-back or face-to-face arrangement.

Dynamic Load Rating: 9,750 N. Static Load Rating: 6,400 N. Both are SKF set ratings covering the two bearings together. Fatigue load limit: 275 N. Ball diameter: 4.762 mm. Number of balls per bearing: 15. Calculation factor for equivalent loads f0: 9.8. Reference grease quantity: 0.45 cm³ per bearing. The set is preload-adjusted at the factory and therefore carries no internal clearance class.

Limiting Speed: 45,000 rpm on grease and 67,000 rpm on oil-air, the SKF single-bearing figures before the arrangement speed reduction factor. For this 719 D series at extra light preload the factors are 0.81 back-to-back, 0.77 face-to-face, and 0.9 for a spring-loaded DT tandem set.

Mounting data

Shoulder diameter of inner ring: 25.6 mm on both the large and small side faces. Shoulder diameter of outer ring, large side face: 31.4 mm. Chamfer dimension r1,2: 0.3 mm minimum. Chamfer dimension r3,4: 0.2 mm minimum. Diameter of shaft abutment da and db: 22 mm minimum. Diameter of housing abutment Da: 35 mm maximum. Diameter of housing abutment Db: 35.6 mm maximum. Radius of fillet ra: 0.3 mm maximum. Radius of fillet rb: 0.2 mm maximum. Position of oil nozzle dn: 26.8 mm.

Quantity and configuration

Mounting Arrangement: universally matchable, back-to-back (DB), face-to-face (DF) or tandem (DT). Arrangement / Configuration: matched set of two at extra light preload. Unit Quantity: 2 Pcs. Cage Type: outer-ring shoulder-guided. Lubricant: none; the bearings are supplied ungreased. Snap ring included: No. Rings are one-piece inner and outer. Contact type: normal contact, two-point.

Interchange guidance

Equivalent 20 x 37 x 9 mm 15° super-precision executions: FAG B71904-C-T-P4S, NSK 7904CTYNSULP4, NTN 7904UCG/GNP4, RHP 7904CTDULP4, Koyo 7904C-5GLFGP4. Preload level and arrangement are carried by separate suffixes in each maker’s own scheme.