NUP311 bearing: complete specifications & equivalents
The NUP311 is a ISO 15 radial bearing sized 55 x 120 x 29 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 29 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 123 kN |
| Basic static load rating C0 | 111 kN |
| Fatigue load limit Pu | 13.6 kN |
| Limiting speed (mechanical) | 5900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1420 g |
| Manufacturer designation | NTN NUP311 |
| 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 & NUP300-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.142 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 mm |
| Smallest bore in NUP300-series | 20 mm |
| Largest outer diameter in NUP300-series | 580 mm |
| Width range across NUP300-series | 15–108 mm |
| Bore position in NUP300-series (smallest first) | 8 of 32 |
| Bore above smallest NUP300-series size | 35 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NUP311-ECP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×120×29 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 NUP311 model number is decoded
For pure radial duty on a 55 mm shaft NTN supplies NUP311: the NJ rib arrangement plus a loose L-shaped rib ring on the inner ring; the open execution is rated 5,900 r/min on grease and 7,000 r/min on oil. Digit by digit, NUP311 reads as NUP (inner ring two ribs + loose L-ring), ISO 15 series, and bore 55 mm; trailing letters such as EA or E mark the cage/capacity execution and are part of the order number. 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 NUP311. Rating life at 123 kN C assumes clean oil and adequate film; the 13.6 kN Pu floor means contamination derating — not the C rating alone — governs adjusted life in dusty gearboxes. After mounting verify the outer ring slides axially by hand at ambient temperature; a stuck float ring in a NUP311 non-locating position preloads the bearing when the shaft grows.
Typical equipment & failure modes
Common applications
- machine-tool gearbox and spindle radial sets
- material-handling drum and wheel shafts
- papermaking and printing auxiliary drives
- fan and blower rotor positions
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
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- hard-particle indentation of raceways in unfiltered oil or open arrangements
- brinelling from static overload or impact during handling
Selection pitfalls — read before you substitute
- On this 55 mm bore, shaft thermal growth can preload the inner ring if the fit is too tight; verify residual interference at temperature and confirm the float ring still slides after mounting NUP311.
- The 29 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 55 mm inner ring.
- Open NUP311 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 55 mm contact.
- The 29 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 55 mm inner ring.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 120 mm race brinells and releases as vibration within hours.
- The 123/111 kN ratings, 13.6 kN Pu and 1420 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NUP311 (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 NUP311?
NUP311 is an NTN NUP single-row cylindrical roller bearing to ISO 15: 55 mm bore, 120 mm OD and 29 mm width (2.165 × 4.724 × 1.142 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 123 kN, C0 111 kN, Pu 13.6 kN, grease limiting speed 5,900 r/min, oil 7,000 r/min, mass about 1420 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. NUP311 is the NJ rib arrangement plus a loose L-shaped rib ring on the inner ring — it locates the shaft in both axial directions.
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. NUP311 is listed among the ＊ ULTAGE-marked executions in 2203E.
Can NUP311 take axial load and locate a shaft?
the NUP design provides two-direction axial location via its loose rib ring, for light/moderate thrust guidance. The loose rib ring still only suits light/short-duration axial guidance; heavy thrust belongs to a dedicated thrust bearing.
What do Fw and Ew mean for NUP311?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 70.5 mm, Ew 104.5 mm. The nominal bore/OD remain 55/120 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 5,900 r/min grease / 7,000 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.