RHPSuper Precision Angular Contact Ball Bearing 55x100x21mm 15 Degree Contact Angle ABEC 5 Machined Phenolic Cage Universally Ground Light Preload – ONE Bearing (Half of a Pair)

Product Description

What this part is

One RHP (now NSK) 7211CTDULP5 super-precision angular contact ball bearing, 55 mm bore x 100 mm outside diameter x 21 mm width. Single row, 15° contact angle, machined phenolic cage, open, ABEC 5 precision, universally ground for light-preload duplex pairing. Also marked on the carton as 7211X2TADULEP5.

Read this first — you are buying ONE bearing:
The -1/2PR suffix means half of a pair, that is one single bearing. The DUL in the designation does not mean two bearings are included. DUL describes how two universally ground rings behave when they are paired — it is a grind specification, not a pack quantity. Quantity supplied is one (1) bearing. A complete duplex set is two units.

Decoding the designation

7211 – ISO base number, 55x100x21 mm boundary dimensions. C – 15° nominal contact angle. T / TA – machined phenolic (textile-laminate) cage. X2 – RHP design variant coding, seen in the alternate 7211X2TADULEP5 marking. DUL – duplex, universally ground, light preload. P5 / EP5 – ABEC 5 precision class (RHP wrote its precision classes with an E prefix; EP7 is ABEC 7, EP5 is ABEC 5). -1/2PR – one half of a pair. One bearing.

Published specifications

Bore: 55 mm, straight. Outside diameter: 100 mm. Width: 21 mm. Contact angle: 15°. Precision class: ABEC 5 / ISO P5 (RHP EP5). Cage: machined one-piece phenolic textile laminate. Closure: open. Preload: light. Rows: 1. Mounting arrangement: universal. Basic dynamic load rating: 56.5 kN. Basic static load rating: 39.5 kN. Limiting speed: 13000 rpm. Maximum operating temperature: 120°C. Minimum operating temperature: -30°C. Item weight: 1.34 lbs. Harmonization code: 8482.10.50.68.

Why universally ground matters more than it sounds

A universally ground bearing has its ring faces relieved to a controlled, symmetrical amount so that any two bearings from the same designation can be stacked in any orientation — back-to-back, face-to-face or in tandem — and will automatically develop the specified preload when the rings are clamped together. That is the practical value of the DUL grind: the arrangement is not fixed at purchase, and no spacer or shim set calculated for the specific pair is required. It also means this single bearing can later be paired with another unit of the same designation, which a non-universal bearing cannot do.

Why 15° and not 25°

The 15° contact angle biases this bearing towards radial stiffness and speed rather than raw thrust capacity. A shallower angle keeps the ball load path closer to the radial plane, reducing centrifugal and gyroscopic effects on the balls and cage, which is why 15° bearings run faster and generate less heat than the 25° and 30° alternatives in the same envelope. The cost is axial capacity and axial stiffness. A 25° or 30° bearing in a position designed around 15° changes the preload force a given clamp-up produces, so it is not an angle-for-angle substitution.

Why preload class must match

Preload class is not a quality grade. Light preload trades stiffness for lower heat generation and higher speed capability; medium and heavy preload buy stiffness at the cost of running temperature and bearing life. A light-preload bearing paired against a medium-preload unit yields neither specification, and the resulting preload is unpredictable.

Interchange guidance

RHP was absorbed into NSK, so RHP to NSK is the obsolescence trail. The corresponding NSK designation family is 7211CTR/7211CTYN with DUL preload and P5 precision. Same-envelope 55x100x21 mm alternatives include SKF 7211 CD/P5 (15°), FAG B7211-C-T-P4S/P5 and NTN 7211C. Interchange is governed by contact angle, precision class, cage material, preload class and universal-grind status as well as by the envelope dimensions.