SKF7211ACDP4ATBTBSuper Precision Angular Contact Ball Bearing Matched Triplex Set – 55 mm ID, 100 mm OD, 21 mm Width, Open, 25° Contact Angle, Medium Preload, Back-to-Back Against a Tandem Pair

Product Description

What this part is

SKF 7211-ACD/P4ATBTB super-precision angular contact ball bearings, supplied as a ready-to-mount matched triplex set. Series: 72, medium section. Bore: 55 mm. Outside Diameter: 100 mm. Width: 21 mm per bearing. Open on both faces, machined fabric-reinforced phenolic resin cage, steel balls on steel raceways. Searchable forms: 7211 ACD/P4ATBTB, 7211ACDP4ATBTB, 7211-ACD-P4A-TBTB, 7211ACD/P4A TBTB.

Decoding the designation

Contact Angle: 25°. Precision Class: P4A — ABEC 7 dimensional tolerance with running accuracy held to ABEC 9. Set configuration: triplex, back-to-back against a tandem pair. Preload: medium. Cage: machined phenolic resin, rated for continuous service to 120°C.

What these specs mean in practice

A back-to-back arrangement takes thrust in both directions and resists moment loading, so it locates a shaft axially in a single bearing position. The tandem pair shares thrust in the primary direction between two rows, roughly doubling axial capacity that way. Per bearing: Dynamic Load Rating 52.7 kN, Static Load Rating 40.5 kN. Limiting speed: 13 000 r/min. Medium preload raises stiffness and holds shaft position more closely than light preload, and generates more heat at speed.

Quantity and configuration

Matched triplex set: two bearings in tandem, the third mounted back-to-back against them. Unit Quantity: 3 Pcs. Open bearings, protected with an oil preservative for storage.

Fitting notes

The bearings are ground as a set and are mounted together in the order and orientation marked on the outer ring faces. The phenolic cage sets the temperature ceiling at 120°C. Preloaded bearings run without internal clearance, so shaft and housing seats are held to super-precision tolerances.

Interchange guidance

Same-envelope equivalent single bearing: FAG B7211-E-T-P4S. SKF 7211 CD/P4ATBTB is a related size at a 15° contact angle. SKF 7211 ACD/P4ATBTA is a related size at light preload.