NJ308 bearing: complete specifications & equivalents
The NJ308 is a ISO 15 radial bearing sized 40 x 90 x 23 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 23 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 65 kN |
| Basic static load rating C0 | 57 kN |
| Fatigue load limit Pu | 6.95 kN |
| Limiting speed (mechanical) | 8000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 643 g |
| Manufacturer designation | NTN NJ308 |
| 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 & NJ300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 0.906 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in NJ300-series | 17 mm |
| Largest outer diameter in NJ300-series | 580 mm |
| Width range across NJ300-series | 14–108 mm |
| Bore position in NJ300-series (smallest first) | 6 of 33 |
| Bore above smallest NJ300-series size | 23 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NJ308-ECP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 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 NJ308 model number is decoded
The NTN order number NJ308 denotes a 40×90×23 mm (1.575 × 3.543 × 0.906 in) cylindrical roller bearing in the NJ300 family, a pressed sheet-steel cage. Reading the code: NJ for the one-direction-locating type, then the ISO 15 diameter/width series and the bore code — ×5 = 40 mm (00–03 use the 10/12/15/17 exception table). 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. Thermal planning around the 8,000 r/min grease ceiling should include the cage type (a pressed sheet-steel cage) and oil-flow option to 9,400 r/min for continuously high-duty 40 mm positions. On NJ 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
- 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
- inner-ring raceway spalling from overload in the line-contact Hertzian zone
- pressed-steel cage pocket wear when rollers skid at light load or too-thin lubricant
- 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
- On this 40 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 NJ308.
- Grease limiting speed 8,000 r/min and oil 9,400 r/min are different limits for NJ308: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- The NJ rib arrangement is not interchangeable with another prefix on the same 40 mm seat: inner ring two ribs + one outer rib. Swapping NU for NJ changes axial location behaviour even though the 90×23 mm envelope matches.
- Do not replace NJ308 with a deep-groove ball bearing on rating alone: line contact gives 65 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 65/57 kN pair here belongs to NJ308 as printed, not to the bare size.
- The 65/57 kN ratings, 6.95 kN Pu and 643 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NJ308 (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 NJ308?
NJ308 is an NTN NJ single-row cylindrical roller bearing to ISO 15: 40 mm bore, 90 mm OD and 23 mm width (1.575 × 3.543 × 0.906 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 65 kN, C0 57 kN, Pu 6.95 kN, grease limiting speed 8,000 r/min, oil 9,400 r/min, mass about 643 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. NJ308 is two integral ribs on the inner ring and one rib on the outer ring — it locates the shaft in one axial direction.
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. NJ308 is listed among the ＊ ULTAGE-marked executions in 2203E.
Can NJ308 take axial load and locate a shaft?
the NJ design accepts axial load in one direction and provides one-way shaft location. For two-direction location use an NUP execution or an NJ pair with loose rib rings.
What do Fw and Ew mean for NJ308?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 53.5 mm, Ew 77.5 mm. The nominal bore/OD remain 40/90 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 8,000 r/min grease / 9,400 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.