MPBHADB-008-13Precision Angular Contact Ball Bearing 40x62x12 mm, Machined Copper-Alloy Cage, Matched Duplex Pair – ISO 7908 / 71908 Envelope

Product Description

What this part is

An MPB precision angular contact ball bearing in the 19-dimension series, 40 mm bore × 62 mm outside diameter × 12 mm width, supplied as a matched duplex pair with a machined copper-alloy cage. MPB Corporation built precision and aerospace-grade bearings under military and OEM part numbers rather than commercial catalogue designations, which is why this part carries a HADB number instead of an ISO one.

Decoding the designation

H — angular contact design with a counterbored outer ring, non-separable.
ADB — angular contact, duplex arrangement. See the configuration note below on which duplex arrangement.
008 — MPB’s internal size code for this envelope.
13 — MPB’s variant or specification code for this build.

Identity confirmed through the NSN chain

This is the useful part for a buyer trying to source a replacement. National stock number 3110-00-249-8996 covers this bearing, and that same NSN lists as approved alternates SKF 7908-VAC and Timken 3MM9308WI, both of which are 40 × 62 × 12 angular contact bearings. Two independent manufacturers’ parts sharing the NSN confirms the envelope and the general type, and confirms the ISO equivalence to a 7908.

On the naming: 7908 is the NSK/JIS style designation for the 19-series 40 × 62 × 12 envelope, and 71908 is the ISO/European designation for the same envelope. Both are correct and both are worth searching. They are dimensionally interchangeable; whether they are specification-interchangeable depends on the contact angle and precision suffix each maker applies, which differ between schemes.

Quantity and configuration

This is a duplex pair — two bearings ground as a matched set. One caution on the arrangement: the ADB designation reads as back-to-back, but the government cataloguing record for this stock number describes the style as face-to-face. Those are opposite arrangements with opposite stiffness and misalignment behaviour, and the conflict is not resolvable from the data. The listing therefore describes the part as a duplex pair without asserting back-to-back or face-to-face. If the arrangement matters to your application, ask for a photograph of the ring faces before ordering — the relative position of the counterbored shoulders on the two rings settles it in seconds.

No pair-count claim is published. Surplus duplex stock is regularly split, so confirm the physical piece count against your requirement.

Published ratings and mounting data

Load ratings, limiting speed, contact angle, precision class and ball complement are not published for HADB-008-13. MPB’s part numbers were issued against customer and military specifications rather than a public catalogue, and no manufacturer data sheet is available for this number. Nothing has been substituted from a similar-looking bearing, because the contact angle in particular cannot be guessed — the same envelope is built at 15°, 25° and 30° depending on the specification, and those are functionally different bearings.

Fitting notes

Keep the matched pair together; the preload is ground into the faces and cannot be recreated by pairing arbitrary bearings. Align the etched face marks as ground. A machined copper-alloy cage tolerates higher temperature than a phenolic cage but is less forgiving of marginal lubrication, so ensure the position is properly lubricated from the outset.

Interchange guidance

Search terms and cross-references that reach this bearing: 7908, 71908, SKF 7908-VAC, Timken 3MM9308WI, and the full carton string 3MM9308WIMBRDUA1035. The vendor number 358529-1 also appears against it. Note that a Timken 3MM9308WI is a 25° bearing by the Fafnir prefix convention, which is suggestive of this part’s angle but is not proof of it, since NSN alternates are approved on function rather than on identical internal geometry. MPB precision bearing operations passed through NN Inc.