NN4944K bearing: complete specifications & equivalents
The NN4944K 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 | 14500 g |
| Manufacturer designation | NTN NN4944K |
| 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 | — |
| 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 |
|---|---|---|---|
| NN4944K | 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 NN4944K model number is decoded
NN4944K is the extra-light (10/49) section of the NTN NN4900 dimension series for a 220 mm shaft — 650 kN of basic dynamic capacity in a 14500 g, open bearing. The leading NN defines the rib arrangement (double row, ribbed inner ring, separable outer); the dimension-series digits and the two-digit bore code resolve to 220 mm, with 300 mm OD and 80 mm width from the ISO 15 general plan. Minimum radial load matters: an unloaded NN4944K at high speed skids its rollers and smears the raceway; spring preload or the rotor weight typically covers the requirement in motors and pumps. The 3.0 kN-per-mm-bore figure (650 kN over 220 mm) lets a NN4944K interchange candidate be screened quickly against the same-envelope ball or roller alternatives. Provide axial location with an adjacent locating bearing rather than expecting the float cylindrical set to hold thrust on the 220 mm shaft.
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
- cage wear accelerated when the EA high-capacity roller complement runs continuously above its thermal balance
- grease starvation and cage drag when relubrication intervals are extended past the grease life
- electrical pitting on VFD-driven motor shafts without grounding protection
- fretting corrosion on a loose rotating shaft seat
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 14500 g NN4944K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NN4944K skids at 1,900 r/min and fails by smearing long before L10 fatigue.
- Grease limiting speed 1,900 r/min and oil 2,200 r/min are different limits for NN4944K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- The NN rib arrangement is not interchangeable with another prefix on the same 220 mm seat: double row, ribbed inner ring, separable outer. Swapping NU for NJ changes axial location behaviour even though the 300×80 mm envelope matches.
- Do not replace NN4944K 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.
- The 650/1300 kN ratings, 118 kN Pu and 14500 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4944K (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 NN4944K?
NN4944K 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 14500 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. NN4944K 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. NN4944K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4944K?
The K suffix denotes a 1:12 tapered bore. NN4944K mounts on a tapered shaft seat or adapter sleeve and is driven up to a measured residual clearance or preload — this is how precision spindle bearings achieve stiffness without locknut guesswork; the cylindrical-bore NN4944 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4944K?
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.