NU211 bearing: complete specifications & equivalents
The NU211 is a ISO 15 radial bearing sized 55 x 100 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | Generic ISO interchange (unbranded) |
| Bore diameter d | 55 mm |
| Outer diameter D | 100 mm |
| Width B | 21 mm |
| Seal / shield | open |
| Internal clearance | CN / C3 / C4 available |
| Tolerance class | P0 |
| Cage | steel |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 587 g |
| Standard | ISO 15 |
| Catalog version | iso15-crb-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for NU211 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & NU200-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.827 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 22.5 mm |
| Smallest bore in NU200-series | 20 mm |
| Largest outer diameter in NU200-series | 180 mm |
| Width range across NU200-series | 14–34 mm |
| Bore position in NU200-series (smallest first) | 8 of 17 |
| Bore above smallest NU200-series size | 35 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU211 model number is decoded
In the NU200-series (ISO 15 dimension series) the leading NU marks a single-row cylindrical roller: the outer ring has two integral shoulders and the inner ring none, so the inner-ring/roller assembly floats axially both ways and the bearing locates radially only; the last two digits of NU211 are bore code 11 = 55 mm (code × 5 from 04 upward). The ISO 15 envelope is 100 mm outside diameter and 21 mm width — 2.165 × 3.937 × 0.827 in, with a 22.5 mm radial section height. Straight cylindrical rollers give line contact for high radial capacity at low friction, with no self-alignment; catalogue practice for a rotating inner ring is a k5 shaft seat, H7 housing and C3 clearance. NJ adds one inner shoulder (one-direction location), NUP two shoulders (full location); E denotes a reinforced roller complement — verify against the actual load direction.
Typical equipment & failure modes
Common applications
- wind turbine gearbox intermediate shafts
- industrial helical and planetary gearboxes
- medium electric motor drives
- centrifugal pump and compressor shafts
- machine tool gearboxes and feed drives
Known failure patterns
- cage fatigue and fracture after sustained over-speed with marginal lubrication
- fretting corrosion on an interference inner-ring seat that creeps under a loose fit
- false brinelling indentations at the roller pitch when an idle bearing sits in machine vibration
- inner-ring shoulder damage from cold mounting force transmitted through the roller set
- thermal seizure when an interference fit plus hot running removes all residual C3 clearance
Selection pitfalls — read before you substitute
- On this 55 mm-bore NU211, set C3 as the default for an interference inner-ring fit and recheck play after mounting; a row that turned freely on the bench can be fully clamped once the 55 mm shaft reaches operating temperature.
- The NU2 light series at 55 mm bore (100×21 mm) is the default gearbox cylindrical row; on the same bore an NU311 is larger with a much higher rating — do not replace a failed NU311 with an NU211 without re-rating L10 life.
- Check the shoulder geometry for NU211: a generous fillet on the 55 mm shaft looks strong but stops the inner ring seating home; use the catalogue corner-relief radius and a withdrawal groove so the outer ring presses flush in the 100 mm, 21 mm-wide housing bore.
- Large NU211 rings need real draw-up force: use a sleeve or hydraulic press against the inner ring face only, verify the 55 mm seat temperature before assembly, and never strike the roller cage — a dented cage window on the 21 mm-wide set locks the rollers at the first hot run.
- When reusing separable NU211 rings, keep the matched pair together and inspect both seats: a crept inner ring frets a polished groove into the 55 mm journal that a new bearing will repeat unless the shaft is repaired or reclaimed.
- The rings of an NU211 are separable and supplied as a matched unit: never mix the outer ring of one bearing with the inner-ring/roller assembly of another — the raceway and roller complement are graded together, and cross-matching shortens life even at identical 55×100 dimensions.
- Apply mounting force to the ring with the interference fit — inner ring for a shaft fit, outer ring for a housing fit; pushing the 55 mm inner ring home through the rollers brinells the 100 mm outer raceway.
Frequently asked questions
What are the dimensions of an NU211 cylindrical roller bearing?
An NU211 single-row cylindrical roller bearing per ISO 15 has a 55 mm bore, 100 mm outer diameter and 21 mm width (2.165 × 3.937 × 0.827 in), a 22.5 mm radial section and roughly 587 g geometry-based estimated mass; catalogue masses vary with cage and E design.
How does the NU211 bore code work?
The letters give the ring/shoulder design (NU = axially free, NJ = one inner shoulder, NUP = two shoulders) and the last two digits are bore code 11: 11 × 5 = 55 mm. The 100 mm OD and 21 mm width come from the ISO 15 dimension series (NU200), which shares its boundary plan with the 6-series deep-groove envelopes.
What is the difference between NU, NJ, N and NUP designs?
NU (like the NU211) has a shoulderless inner ring and floats axially in both directions; NJ has one integral inner-ring shoulder and locates the shaft in one direction; N has two inner shoulders and a shoulderless outer ring (mirror of NU); NUP adds a second, loose shoulder so the inner ring locates in both directions. Select by the shaft locating scheme, not by load rating — the envelopes are identical.
Can an NU211 take axial load or misalignment?
No thrust in the NU design: any sustained axial force scores the roller ends and ring flanges, so locate the shaft with an NJ/NUP row, a paired angular-contact bearing or a deep-groove row elsewhere. Misalignment is likewise not tolerated — line contact between cylindrical rollers and raceways edges under even small angular errors; use a spherical roller bearing where shaft deflection or housing misalignment is expected.
What does the E suffix mean and which clearance should be ordered?
E (as in NU211E) is the reinforced design: larger/optimised rollers raise the basic load rating over the basic designation in the same 55×100×21 mm envelope. For clearance, C3 is the usual default with an interference fit on a rotating inner ring because fit and thermal growth reduce residual play; use CN mainly for loose floating outer-ring mounts and C4 for hot or vibratory duty.
Reviewed & verified by the MPN Base engineering desk against source catalog iso15-crb-geometry on 2026-09-24. Read our editorial & correction policy.