NN4944 bearing: complete specifications & equivalents
The NN4944 is a ISO 15 radial bearing sized 220 x 300 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 | 220 mm |
| Outer diameter D | 300 mm |
| Width B | 80 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 650 kN |
| Basic static load rating C0 | 1300 kN |
| Fatigue load limit Pu | 118 kN |
| Limiting speed (mechanical) | 1900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 15200 g |
| Manufacturer designation | NTN NN4944 |
| 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 & NN4900-series range
| Bore d | 8.661 in |
|---|---|
| Outer diameter D | 11.811 in |
| Width B | 3.15 in |
| ISO bore code | 44 |
| Radial section height (D−d)/2 | 40 mm |
| Smallest bore in NN4900-series | 100 mm |
| Largest outer diameter in NN4900-series | 440 mm |
| Width range across NN4900-series | 40–118 mm |
| Bore position in NN4900-series (smallest first) | 13 of 18 |
| Bore above smallest NN4900-series size | 120 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4944 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
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 NN4944 model number is decoded
NN4944 belongs to the NTN cylindrical roller range in NTN Ball and Roller Bearings CAT.No.2203E: line-contact rollers between ground raceways for a 650 kN dynamic rating in the 220 mm bore. On the NTN nameplate NN states which ring carries the ribs, which determines whether NN4944 floats or locates; the numeric remainder is the ISO 15 series and 220 mm bore reference, not a fit or clearance instruction. Double-row NN precision cylindrical roller bearing: ribbed inner ring with a separable outer ring, two roller rows for high radial stiffness on machine-tool spindles; precision classes P5/P4/P2 and clearance are ordered separately. Rating life at 650 kN C assumes clean oil and adequate film; the 118 kN Pu floor means contamination derating — not the C rating alone — governs adjusted life in dusty gearboxes. On NN 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
- high-speed turbine and turbo-blower rotor supports
- coordinate-measuring and semiconductor-equipment drives
- machine-tool main spindles requiring high radial stiffness
- precision gearbox and indexing-drive shafts
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
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- rolling-contact fatigue after the catalogue L10 life is exceeded
- electrical pitting on VFD-driven motor shafts without grounding protection
Selection pitfalls — read before you substitute
- At 220 mm bore, oil-lubricated arrangements toward 2,200 r/min need positive flow and drain design; the 15200 g NN4944 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Do not replace NN4944 with a deep-groove ball bearing on rating alone: line contact gives 650 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 300 mm race brinells and releases as vibration within hours.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 300 mm race brinells and releases as vibration within hours.
- 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 220 mm inner ring.
- The 650/1300 kN ratings, 118 kN Pu and 15200 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4944 (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 NN4944?
NN4944 is an NTN NN double-row precision cylindrical roller bearing to ISO 15: 220 mm bore, 300 mm OD and 80 mm width (8.661 × 11.811 × 3.15 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 650 kN, C0 1300 kN, Pu 118 kN, grease limiting speed 1,900 r/min, oil 2,200 r/min, mass about 15200 g. It is open, with a machined or stamped steel cage per the precision execution.
What is the difference between NU, NJ, NUP, N and NF cylindrical roller bearings?
NN and NNU are double-row precision designs rather than single-row rib variants: NN has a ribbed inner ring and separable outer ring, NNU the reverse; both give high radial stiffness for spindles and are commonly ordered with P5/P4 precision and a K 1:12 tapered bore for preload setting. NN4944 is the NN execution.
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. NN4944 is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4944?
NN4944 has a cylindrical bore and mounts on a plain machined shaft seat; a K execution (1:12 taper) exists in the NN4900 series when preload must be set by drive-up on a tapered seat.
What do Fw and Ew mean for NN4944?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 245 mm. The nominal bore/OD remain 220/300 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.