SNRSuper Precision Angular Contact Spindle Bearing Matched Pair 20 x 42 x 12 mm 25 Degree Contact Angle ABEC 7 P4 Universally Ground Phenolic Cage

Product Description

What this part is

SNR 7004HG1DUJ84 super-precision single-row angular contact ball bearings, supplied as a matched universally ground pair. Brand: SNR (now NTN-SNR). Bore: 20 mm. Outside Diameter: 42 mm. Width: 12 mm per bearing. Total Width: 24 mm for the pair. Contact Angle: 25°. Preload: Medium. Precision Class: ISO 4, P4, ABEC 7. Cage Material: fabric-reinforced phenolic laminate. Cage Type: machined, centred on the outer ring. Bearing Material: 52100 vacuum-degassed steel rings and balls. Rolling Elements: steel balls. Closure Type: open. Lubricant: grease or oil. Unit Quantity: 2 Pcs, one matched DU pair. The set is preload-set at manufacture rather than clearance-set. Series: 70. Base Number: 7004. Carton date code 05 1989, factory new old stock.

Decoding the designation

7004: 70-series single-row angular contact ball bearing on a 20 mm bore. H: 25° contact angle in SNR’s designation scheme. G1: SNR high-load-capacity version code. DU: a pair of universal bearings. J84: the 8 is the preload grade, medium; the 4 is the precision class, ISO 4 / P4 / ABEC 7. F20 and the outer-ring sequence marks 1 and 2 are SNR pair-matching marks identifying these two rings as ground and measured as one set. Searchable forms: 7004HG1DUJ84, 7004 H G1 DU J84, 7004-H-G1-DU-J84, 7004.H.G1.DU.J84, and the world equivalent 7004-E-T-DUM-P4.

What these specs mean in practice

A 25° contact angle tilts the load path further toward the bearing axis than a 15° angle, giving higher thrust capacity and higher axial stiffness, so a spindle holds size better under heavier and interrupted cuts. The trade is speed: the steeper angle raises centrifugal and gyroscopic ball loading, so heat generation is higher than an otherwise identical 15° bearing. 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. Fabric-reinforced phenolic is light, self-lubricating and tolerant of marginal lubrication, which is why it remains standard on machine-tool spindle bearings. 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.

Quantity and configuration

Unit Quantity: 2 bearings, one matched DU pair. Universal grinding means any two bearings of this designation pair in any orientation and come up to the intended preload when clamped, with no shims 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. Both bearings are individually shrink-wrapped in factory preservative, with two SNR cartons and the original SNR French-language mounting instruction sheet for precision angular contact bearings.

Mounting data

The outer rings carry etched sequence marks 1 and 2 identifying pair order. The press fit belongs on the rotating ring. Clamping is uniform, through a faced nut or spacer, so load passes through the rings rather than the balls. A 25° medium-preload pair generates more heat than a light-preload or 15° execution of the same size.

Interchange guidance

SNR bearing operations merged into NTN-SNR, so current-catalogue equivalents are listed under NTN-SNR. Same-envelope 20 x 42 x 12 mm, 25°, P4 universally ground alternatives: NSK 7004A5TYNDUMP4 (A5 = 25°), FAG / Schaeffler B7004-E-T-P4S-UM, and SKF 7004 ACD/P4ADGA (AC = 25°). Preload class matches within a single spindle stack, and this set is the medium grade. A 15° execution is a related size rather than an interchange, since axial stiffness differs.