NU256 bearing: complete specifications & equivalents
The NU256 is a ISO 15 radial bearing sized 280 x 500 x 80 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 280 mm |
| Outer diameter D | 500 mm |
| Width B | 80 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1320 kN |
| Basic static load rating C0 | 1760 kN |
| Fatigue load limit Pu | 143 kN |
| Limiting speed (mechanical) | 1200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 69400 g |
| Manufacturer designation | NTN NU256 |
| 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 | 11.024 in |
|---|---|
| Outer diameter D | 19.685 in |
| Width B | 3.15 in |
| ISO bore code | 56 |
| Radial section height (D−d)/2 | 110 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) | 34 of 36 |
| Bore above smallest NU200-series size | 265 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU256-MA | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 280×500×80 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 NU256 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NU256 appears as a 280 mm bore single-row cylindrical roller bearing (1320 kN C / 1760 kN C0) with a pressed sheet-steel cage, listed to the ISO 15 boundary plan. Digit by digit, NU256 reads as NU (outer ring ribbed, inner ring ribless), ISO 15 series, and bore 280 mm; trailing letters such as EA or E mark the cage/capacity execution and are part of the order number. The separable ring comes off without removing the roller assembly from the other ring, which eases inspection and lets the non-locating arrangement accommodate thermal shaft growth — the NU design floats on both sides. With the inner ring rotating, catalogue practice is a m6/n6 shaft seat and an H7/H6 housing; the outer ring must remain free to creep slightly axially in non-locating NU arrangements. On NU arrangements confirm which ring is separable before heating: forcing the ribbed ring off over the roller complement damages the cage and rib faces.
Typical equipment & failure modes
Common applications
- offshore drawworks and winch drums
- heavy press and large gearbox main shafts
- rolling-mill work-roll and backup-roll positions
- large turbine and generator rotor bearings
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
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
Selection pitfalls — read before you substitute
- At 280 mm bore, oil-lubricated arrangements toward 1,400 r/min need positive flow and drain design; the 69400 g NU256 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- If the shaft must be located both ways, do not use NU256 alone: pair it with a locating bearing or specify the NUP execution with the matching loose rib ring from the 2203E table.
- The 80 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 280 mm inner ring.
- The NU rib arrangement is not interchangeable with another prefix on the same 280 mm seat: outer ring ribbed, inner ring ribless. Swapping NU for NJ changes axial location behaviour even though the 500×80 mm envelope matches.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 1320/1760 kN pair here belongs to NU256 as printed, not to the bare size.
- The 1320/1760 kN ratings, 143 kN Pu and 69400 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU256 (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 NU256?
NU256 is an NTN NU single-row cylindrical roller bearing to ISO 15: 280 mm bore, 500 mm OD and 80 mm width (11.024 × 19.685 × 3.15 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1320 kN, C0 1760 kN, Pu 143 kN, grease limiting speed 1,200 r/min, oil 1,400 r/min, mass about 69400 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. NU256 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. NU256 is supplied in the standard open execution shown in the table.
Can NU256 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 NU256?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 340 mm, Ew 440 mm. The nominal bore/OD remain 280/500 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,200 r/min grease / 1,400 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.