RHP7011ETDUMP4Super Precision Angular Contact Ball Bearing 55x90x18 mm, 25 Degree Contact Angle, ABEC 7, Medium Preload, Phenolic Cage, Half of Duplex Pair

Product Description

What this part is

A single super precision angular contact ball bearing in the ISO 70 light series, 55 mm bore, 90 mm outside diameter, 18 mm width. It is a universally ground bearing intended to be assembled against a mating bearing to form a preloaded duplex set, and it is supplied here as one bearing only.

Decoding the designation

7011 — ISO 70 (light) series angular contact ball bearing, 55 x 90 x 18 mm.
E — RHP contact angle code for 25°.
T — phenolic machined cage.
DUM — Duplex, Universally ground, Medium preload.
P4 — ABEC 7 tolerance class.
-1/2PR — half of a pair. This is the single most important part of the number: it means one bearing, not two.

What these specs mean in practice

A 25° contact angle sits in the middle of the super precision range. Against a 15° bearing it carries substantially more thrust and gives higher axial stiffness, but it gives away limiting speed and runs warmer at the same duty. Medium preload is the general purpose choice for machine tool spindles — enough rigidity to hold a bore or a face tolerance under cutting load, without the heat generation that heavy preload brings. The phenolic cage is a genuine high speed feature: it is light, it holds oil in its own porosity, and it is far more forgiving of marginal lubrication than a steel cage.

Quantity and configuration

This SKU is ONE bearing. Universally ground bearings can be mounted back-to-back, face-to-face or in tandem, and the ground offset on the rings sets the preload automatically when two are clamped together — so a second matching 7011E-T-P4 bearing is required to realise the DUM medium preload the number describes. A buyer expecting a two-bearing pair from a designation containing DUM is the classic dispute on this family, which is why the quantity is stated in the title, the scan line and the Unit Quantity attribute.

Fitting notes

Universally ground bearings must be mounted with the ring reference marks aligned as the manufacturer intended; reversing one ring destroys the preload scheme. Do not mix a P4 bearing with a lower class bearing in the same set, and do not mix contact angles — a 15° bearing clamped against a 25° bearing loads unevenly and will fail early. Clean, filtered lubricant is not optional at this tolerance class.

Published ratings and mounting data

Dynamic and static load ratings and the limiting speed are not published by the manufacturer for this exact suffix combination in any source we could verify, so they are deliberately left blank rather than borrowed from a sibling designation. Ratings for a 7011 in a different tolerance class, cage or preload are not this bearing’s ratings.

Interchange guidance

RHP super precision production passed to NSK, so the modern equivalent is sought under NSK numbering. Same envelope 25° super precision alternatives are found as 7011A5 (NSK 25°), B7011E-T-P4S (FAG) and 7011ACD/P4A (SKF). Treat all of these as envelope matches to be confirmed against your preload and mounting scheme, not as drop in equals.