NU238 bearing: complete specifications & equivalents
The NU238 is a ISO 15 radial bearing sized 190 x 340 x 55 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 190 mm |
| Outer diameter D | 340 mm |
| Width B | 55 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 615 kN |
| Basic static load rating C0 | 770 kN |
| Fatigue load limit Pu | 70 kN |
| Limiting speed (mechanical) | 1900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 20800 g |
| Manufacturer designation | NTN NU238 |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & NU200-series range
| Bore d | 7.48 in |
|---|---|
| Outer diameter D | 13.386 in |
| Width B | 2.165 in |
| ISO bore code | 38 |
| Radial section height (D−d)/2 | 75 mm |
| Smallest bore in NU200-series | 15 mm |
| Largest outer diameter in NU200-series | 580 mm |
| Width range across NU200-series | 11–92 mm |
| Bore position in NU200-series (smallest first) | 29 of 36 |
| Bore above smallest NU200-series size | 175 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU238-ECML | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 190×340×55 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the NU238 model number is decoded
For pure radial duty on a 190 mm shaft NTN supplies NU238: two integral ribs on the outer ring and a ribless, separable inner ring; the open execution is rated 1,900 r/min on grease and 2,200 r/min on oil. Reading the code: NU for the non-locating separable-inner-ring type, then the ISO 15 diameter/width series and the bore code — ×5 = 190 mm (00–03 use the 10/12/15/17 exception table). The 75.0 mm radial section ((340−190)/2) frames the roller complement; capacity per millimetre of bore is about 3.2 kN/mm before application factors. The 190 mm (7.48 in) bore and 340 mm (13.386 in) OD are ISO 15 boundary values; fillet and shoulder dimensions must still come from the NTN mounting table for the 55 mm-wide ring. Housing and shaft fillets must clear the ring chamfers of NU238; an oversized radius locks the ring on its face and tilts the 55 mm-wide seat.
Typical equipment & failure modes
Common applications
- rolling-mill work-roll and backup-roll positions
- large turbine and generator rotor bearings
- wind-turbine gearbox planet and rotor shafts
- ship propulsion line shafts and reduction gears
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- cage distortion after a mounting blow carried through the roller set
- grease starvation and cage drag when relubrication intervals are extended past the grease life
- electrical pitting on VFD-driven motor shafts without grounding protection
- false brinelling on standby machines exposed to external vibration
Selection pitfalls — read before you substitute
- At 190 mm bore, oil-lubricated arrangements toward 2,200 r/min need positive flow and drain design; the 20800 g NU238 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NU238 skids at 1,900 r/min and fails by smearing long before L10 fatigue.
- Do not replace NU238 with a deep-groove ball bearing on rating alone: line contact gives 615 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- Open NU238 units need application-supplied sealing and a defined lubricant schedule; film thickness is the first failure mode for line contact when viscosity drops at the 190 mm contact.
- The 75.0 mm section at 190 mm bore leaves a narrow oil path; with the standard cage the relubrication groove and oil-level design must keep grease from churning in the 55 mm-wide cavity.
- The 615/770 kN ratings, 70 kN Pu and 20800 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU238 (standard execution); other makes sharing the ISO 15 envelope revise internal geometry without changing the order number, so keep the 2203E reference with the specification for critical drives.
Frequently asked questions
What are the dimensions and catalogue data of NU238?
NU238 is an NTN NU single-row cylindrical roller bearing to ISO 15: 190 mm bore, 340 mm OD and 55 mm width (7.48 × 13.386 × 2.165 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 615 kN, C0 770 kN, Pu 70 kN, grease limiting speed 1,900 r/min, oil 2,200 r/min, mass about 20800 g. It is open, with a pressed sheet-steel cage.
What is the difference between NU, NJ, NUP, N and NF cylindrical roller bearings?
The prefix states the rib arrangement: NU has two outer-ring ribs and a ribless inner ring (float, no axial load); NJ adds ribs for one-direction location; NUP adds a loose L-ring to locate both directions; N has two inner-ring ribs and a separable outer ring; NF has one rib per ring for one-direction guidance. NU238 is two integral ribs on the outer ring and a ribless, separable inner ring — a non-locating bearing that lets the shaft float axially.
What do the EA, E and ＊ suffixes mean on NTN cylindrical roller bearings?
EA is NTN's high-capacity design with a pressed sheet-steel cage and optimised roller complement in the same ISO 15 envelope; E marks the high-capacity design at the larger bores; the ＊ symbol printed before the code in the NTN catalogue marks the ULTAGE new-generation specification and is not typed as part of the order number. NU238 is supplied in the standard open execution shown in the table.
Can NU238 take axial load and locate a shaft?
the NU design carries no axial load and floats axially on both sides. Provide axial location with an adjacent locating bearing (angular-contact, deep-groove or a paired NJ/NUP set).
What do Fw and Ew mean for NU238?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 231 mm, Ew 299 mm. The nominal bore/OD remain 190/340 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,900 r/min grease / 2,200 r/min oil.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.