NN4948K bearing: complete specifications & equivalents
The NN4948K is a ISO 15 radial bearing sized 240 x 320 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 | 240 mm |
| Outer diameter D | 320 mm |
| Width B | 80 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 680 kN |
| Basic static load rating C0 | 1410 kN |
| Fatigue load limit Pu | 126 kN |
| Limiting speed (mechanical) | 1700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 15600 g |
| Manufacturer designation | NTN NN4948K |
| 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 | 9.449 in |
|---|---|
| Outer diameter D | 12.598 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) | 14 of 18 |
| Bore above smallest NN4900-series size | 140 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4948K | 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 NN4948K model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NN4948K appears as a 240 mm bore single-row cylindrical roller bearing (680 kN C / 1410 kN C0) with a machined or stamped steel cage per the precision execution, listed to the ISO 15 boundary plan. Numbering ties NN4948K to its envelope: type code NN, series NN4900, 240 mm bore; the 320×80 mm outline therefore swaps dimensionally with other ISO 15 bearings of the same code, though rib arrangements differ by prefix. 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. The 240 mm (9.449 in) bore and 320 mm (12.598 in) OD are ISO 15 boundary values; fillet and shoulder dimensions must still come from the NTN mounting table for the 80 mm-wide ring. Housing and shaft fillets must clear the ring chamfers of NN4948K; an oversized radius locks the ring on its face and tilts the 80 mm-wide seat.
Typical equipment & failure modes
Common applications
- high-rpm motorised grinding and milling spindles
- CNC lathe and machining-centre spindle radial sets
- precision rotary-table and dividing-head bearings
- high-speed turbine and turbo-blower rotor supports
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
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- fretting corrosion on a loose rotating shaft seat
- rolling-contact fatigue after the catalogue L10 life is exceeded
Selection pitfalls — read before you substitute
- At 240 mm bore, oil-lubricated arrangements toward 2,000 r/min need positive flow and drain design; the 15600 g NN4948K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Wide (22/23) and light (10/49) executions at 240 mm bore share bore but not OD/width; check the full NN4900 series code before substituting, because housing and shoulder geometry will not interchange.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NN4948K skids at 1,700 r/min and fails by smearing long before L10 fatigue.
- Wide (22/23) and light (10/49) executions at 240 mm bore share bore but not OD/width; check the full NN4900 series code before substituting, because housing and shoulder geometry will not interchange.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 680/1410 kN pair here belongs to NN4948K as printed, not to the bare size.
- The 680/1410 kN ratings, 126 kN Pu and 15600 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4948K (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 NN4948K?
NN4948K is an NTN NN double-row precision cylindrical roller bearing to ISO 15: 240 mm bore, 320 mm OD and 80 mm width (9.449 × 12.598 × 3.15 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 680 kN, C0 1410 kN, Pu 126 kN, grease limiting speed 1,700 r/min, oil 2,000 r/min, mass about 15600 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. NN4948K 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. NN4948K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4948K?
The K suffix denotes a 1:12 tapered bore. NN4948K 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 NN4948 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4948K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 265 mm. The nominal bore/OD remain 240/320 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 1,700 r/min grease / 2,000 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.