NN4924K bearing: complete specifications & equivalents
The NN4924K is a ISO 15 radial bearing sized 120 x 165 x 45 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 120 mm |
| Outer diameter D | 165 mm |
| Width B | 45 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 203 kN |
| Basic static load rating C0 | 360 kN |
| Fatigue load limit Pu | 39.5 kN |
| Limiting speed (mechanical) | 3600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2510 g |
| Manufacturer designation | NTN NN4924K |
| 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 | 4.724 in |
|---|---|
| Outer diameter D | 6.496 in |
| Width B | 1.772 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 22.5 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) | 4 of 18 |
| Bore above smallest NN4900-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4924K | 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 NN4924K model number is decoded
NN4924K belongs to the NTN cylindrical roller range in NTN Ball and Roller Bearings CAT.No.2203E: line-contact rollers between ground raceways for a 203 kN dynamic rating in the 120 mm bore. On the NTN nameplate NN states which ring carries the ribs, which determines whether NN4924K floats or locates; the numeric remainder is the ISO 15 series and 120 mm bore reference, not a fit or clearance instruction. With C 203 kN and C0 360 kN (C0/C ≈ 1.77) the bearing is proportioned for heavy radial load; the NU design carries no axial load and floats axially on both sides. Speed ratio check: limiting 3,600 r/min is .86 of the 4,200 r/min oil value for NN4924K; grease-churn heating closes that gap as fill quantity rises. Housing and shaft fillets must clear the ring chamfers of NN4924K; an oversized radius locks the ring on its face and tilts the 45 mm-wide seat.
Typical equipment & failure modes
Common applications
- precision gearbox and indexing-drive shafts
- high-rpm motorised grinding and milling spindles
- CNC lathe and machining-centre spindle radial sets
- precision rotary-table and dividing-head bearings
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
- brinelling from static overload or impact during handling
- electrical pitting on VFD-driven motor shafts without grounding protection
Selection pitfalls — read before you substitute
- At 120 mm bore, oil-lubricated arrangements toward 4,200 r/min need positive flow and drain design; the 2510 g NN4924K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The 22.5 mm section at 120 mm bore leaves a narrow oil path; with the standard cage the relubrication groove and oil-level design must keep grease from churning in the 45 mm-wide cavity.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NN4924K skids at 3,600 r/min and fails by smearing long before L10 fatigue.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NN4924K skids at 3,600 r/min and fails by smearing long before L10 fatigue.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NN4924K skids at 3,600 r/min and fails by smearing long before L10 fatigue.
- The 203/360 kN ratings, 39.5 kN Pu and 2510 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4924K (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 NN4924K?
NN4924K is an NTN NN double-row precision cylindrical roller bearing to ISO 15: 120 mm bore, 165 mm OD and 45 mm width (4.724 × 6.496 × 1.772 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 203 kN, C0 360 kN, Pu 39.5 kN, grease limiting speed 3,600 r/min, oil 4,200 r/min, mass about 2510 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. NN4924K 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. NN4924K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4924K?
The K suffix denotes a 1:12 tapered bore. NN4924K 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 NN4924 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4924K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 134.5 mm. The nominal bore/OD remain 120/165 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 3,600 r/min grease / 4,200 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.