SNR7008HG1DUJ84Super Precision Angular Contact Bearing Pair 40x68x15 mm 25° Duplex Universally Ground

Product Description

What this part is

SNR 7008HG1DUJ84 super-precision single-row angular contact ball bearings, supplied as a universally ground duplex pair. Brand: SNR (now NTN-SNR). Series: 70. Base Number: 7008. Bore: 40 mm (1.5748 in). Outside Diameter: 68 mm (2.6772 in). Width: 15 mm (0.5906 in) per bearing. Total Width: 30 mm as a duplex pair. Contact Angle: 25°. Precision Class: ISO 4, P4, ABEC 7. Running Accuracy: P4 radial and axial runout. Preload: Medium, 119 lbf. Dynamic Load Rating: 20.51 kN (4,610 lbf) per bearing. Static Load Rating: 16.01 kN (3,600 lbf) per bearing. Limiting Speed: 20,000 rpm on grease, 30,000 rpm on oil, per single bearing. Cage Material: laminated phenolic resin. Cage Type: machined, centred on the outer ring. Bearing Material: 52100 vacuum-degassed steel rings and balls. Rolling Elements: steel balls. Bore Type: straight. Closure Type: open, both faces. Number Of Rows: 1 per bearing. Internal Clearance: N/A — the set is preloaded rather than clearance-set. Lubricant: grease or oil. Item weight: 0.42 lbs. Unit Quantity: 2 Pcs, one matched duplex set.

Decoding the designation

70: the 70 dimension series. 08: 40 mm bore code. H: 25° contact angle. DU: a pair of universal bearings, selected so that bore and outside-diameter variation across the set stays within half the ISO tolerance. J: the character preceding the preload and precision codes. 8: medium preload. 4: precision class ISO 4, ABEC 7, P4. G1 is carried on the carton and is kept as a marking variant. Searchable forms: 7008HG1DUJ84, 7008 H G1 DU J84, 7008-H-G1-DU-J84, 7008.H.G1.DU.J84, and the world equivalent 7008-E-T-DUM-P4.

What these specs mean in practice

A 25° contact angle gives high axial rigidity and thrust capacity for a given envelope, which is what a boring or milling spindle needs when the cut pushes along the axis. The 15° build of the same size spins faster and deflects more axially: on this envelope it is rated 4,860 lbf dynamic and turns 21,000 rpm on grease, against this bearing’s 4,610 lbf and 20,000 rpm. Medium preload sits between the light grade chosen for speed and the heavy grade chosen for maximum rigidity, giving spindle stiffness without the thermal penalty of the heavy grade. Laminated phenolic is light, self-lubricating and tolerant of marginal lubrication, and its low mass reduces cage loading at speed. Rings and balls are 52100 vacuum-degassed steel, a high-carbon chrome bearing steel. ISO 4 gives tighter running accuracy and lower running vibration than standard tolerance, and most SNR ISO 4 bearings achieve ISO 2 run-out accuracy.

Speed ratings

Limiting Speed: 20,000 rpm on grease and 30,000 rpm on oil, both figures for a single bearing. Speed changes when bearings are matched into an arrangement. A back-to-back pair at medium preload runs at 0.70 of the single-bearing figure, giving 14,000 rpm on grease and 21,000 rpm on oil. A face-to-face pair at medium preload runs at 0.65, giving 13,000 rpm on grease and 19,500 rpm on oil.

Quantity and configuration

Unit Quantity: 2 Pcs — one matched duplex universal set. Universal grinding leaves the inner and outer ring faces flush once preloaded, so any two bearings of this designation pair in any orientation and come up to the intended medium preload when clamped, with no ground spacers and no matched-set paperwork. The pair mounts back-to-back (DB) for maximum moment stiffness and two-direction thrust, face-to-face (DF) for tolerance of shaft-to-housing misalignment, or in tandem (DT) to double thrust capacity in one direction.

Interchange guidance

Same-envelope 40 x 68 x 15 mm, 25°, P4 universally ground alternatives at medium preload: FAG / Schaeffler 7008-E-T-P4-DUM, NSK 7008A5TYNDUMP4, SKF 7008 ACD/P4ADGB, and Timken Fafnir 3MM9108WI-DUM. In the SKF scheme DGB is the medium preload grade, and in the NSK scheme A5 is the 25° angle. Preload class matches within a single spindle stack, and this set is the medium grade. A 15° execution, coded C in the SNR and NSK schemes, is a related size rather than an interchange, since contact angle changes both axial stiffness and the load ratings.