NU326 bearing: complete specifications & equivalents
The NU326 is a ISO 15 radial bearing sized 130 x 280 x 58 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 130 mm |
| Outer diameter D | 280 mm |
| Width B | 58 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 620 kN |
| Basic static load rating C0 | 665 kN |
| Fatigue load limit Pu | 65.5 kN |
| Limiting speed (mechanical) | 2500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 17000 g |
| Manufacturer designation | NTN NU326 |
| 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 & NU300-series range
| Bore d | 5.118 in |
|---|---|
| Outer diameter D | 11.024 in |
| Width B | 2.283 in |
| ISO bore code | 26 |
| Radial section height (D−d)/2 | 75 mm |
| Smallest bore in NU300-series | 17 mm |
| Largest outer diameter in NU300-series | 620 mm |
| Width range across NU300-series | 14–109 mm |
| Bore position in NU300-series (smallest first) | 22 of 34 |
| Bore above smallest NU300-series size | 113 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU326-ECP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 130×280×58 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 NU326 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NU326 appears as a 130 mm bore single-row cylindrical roller bearing (620 kN C / 665 kN C0) with a pressed sheet-steel cage, listed to the ISO 15 boundary plan. Reading the code: NU for the non-locating separable-inner-ring type, then the ISO 15 diameter/width series and the bore code — ×5 = 130 mm (00–03 use the 10/12/15/17 exception table). NTN ships these bearings open with normal (CN) radial clearance and P0 tolerance as standard; precision classes and C3/C4 clearance are separate order suffixes, not part of NU326. Speed ratio check: limiting 2,500 r/min is .86 of the 2,900 r/min oil value for NU326; grease-churn heating closes that gap as fill quantity rises. After mounting verify the outer ring slides axially by hand at ambient temperature; a stuck float ring in a NU326 non-locating position preloads the bearing when the shaft grows.
Typical equipment & failure modes
Common applications
- large turbine and generator rotor bearings
- wind-turbine gearbox planet and rotor shafts
- ship propulsion line shafts and reduction gears
- mining SAG/ball-mill drive shafts
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- cage wear accelerated when the EA high-capacity roller complement runs continuously above its thermal balance
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- brinelling from static overload or impact during handling
- hard-particle indentation of raceways in unfiltered oil or open arrangements
Selection pitfalls — read before you substitute
- At 130 mm bore, oil-lubricated arrangements toward 2,900 r/min need positive flow and drain design; the 17000 g NU326 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The 58 mm width and abutment faces must be square to the axis; a tilted spacer concentrates load across the roller set and shows as uneven raceway polish on the 130 mm inner ring.
- Grease limiting speed 2,500 r/min and oil 2,900 r/min are different limits for NU326: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- Open NU326 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 130 mm contact.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 280 mm race brinells and releases as vibration within hours.
- The 620/665 kN ratings, 65.5 kN Pu and 17000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU326 (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 NU326?
NU326 is an NTN NU single-row cylindrical roller bearing to ISO 15: 130 mm bore, 280 mm OD and 58 mm width (5.118 × 11.024 × 2.283 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 620 kN, C0 665 kN, Pu 65.5 kN, grease limiting speed 2,500 r/min, oil 2,900 r/min, mass about 17000 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. NU326 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. NU326 is supplied in the standard open execution shown in the table.
Can NU326 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 NU326?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 167 mm, Ew 243 mm. The nominal bore/OD remain 130/280 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 2,500 r/min grease / 2,900 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.