NU2308 bearing: complete specifications & equivalents
The NU2308 is a ISO 15 radial bearing sized 40 x 90 x 33 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 | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 33 mm |
| Seal / shield | open |
| Internal clearance | CN / C3 / C4 available |
| Tolerance class | P0 |
| Cage | steel |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 860 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 NU2308 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & NU2300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 1.299 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in NU2300-series | 25 mm |
| Largest outer diameter in NU2300-series | 130 mm |
| Width range across NU2300-series | 24–46 mm |
| Bore position in NU2300-series (smallest first) | 4 of 8 |
| Bore above smallest NU2300-series size | 15 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NU2308 model number is decoded
In the NU2300-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 NU2308 are bore code 08 = 40 mm (code × 5 from 04 upward). The ISO 15 envelope is 90 mm outside diameter and 33 mm width — 1.575 × 3.543 × 1.299 in, with a 25.0 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
- centrifugal pump and compressor shafts
- machine tool gearboxes and feed drives
- conveyor and hoist gearcase shafts
- wind turbine gearbox intermediate shafts
- industrial helical and planetary gearboxes
Known failure patterns
- edge loading and rib spalling from shaft-to-housing misalignment — cylindrical rollers run on line contact and cannot self-align
- roller-end and flange scoring when an NU bearing is forced to locate axially; only NJ/NUP designs carry thrust at the shoulders
- 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
Selection pitfalls — read before you substitute
- On this 40 mm-bore NU2308, 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 40 mm shaft reaches operating temperature.
- The NU23 wide medium series (40×90×33 mm) packs the highest rating of the 40 mm-bore cylindrical rows into the NU3 housing bore; the 25.0 mm section and wide roller set tolerate no misalignment, so align the seats before selecting it over an NU308.
- Check the shoulder geometry for NU2308: a generous fillet on the 40 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 90 mm, 33 mm-wide housing bore.
- Large NU2308 rings need real draw-up force: use a sleeve or hydraulic press against the inner ring face only, verify the 40 mm seat temperature before assembly, and never strike the roller cage — a dented cage window on the 33 mm-wide set locks the rollers at the first hot run.
- When reusing separable NU2308 rings, keep the matched pair together and inspect both seats: a crept inner ring frets a polished groove into the 40 mm journal that a new bearing will repeat unless the shaft is repaired or reclaimed.
- The rings of an NU2308 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 40×90 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 40 mm inner ring home through the rollers brinells the 90 mm outer raceway.
Frequently asked questions
What are the dimensions of an NU2308 cylindrical roller bearing?
An NU2308 single-row cylindrical roller bearing per ISO 15 has a 40 mm bore, 90 mm outer diameter and 33 mm width (1.575 × 3.543 × 1.299 in), a 25.0 mm radial section and roughly 860 g geometry-based estimated mass; catalogue masses vary with cage and E design.
How does the NU2308 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 08: 08 × 5 = 40 mm. The 90 mm OD and 33 mm width come from the ISO 15 dimension series (NU2300), 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 NU2308) 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 NU2308 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 NU2308E) is the reinforced design: larger/optimised rollers raise the basic load rating over the basic designation in the same 40×90×33 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.