NN4934K bearing: complete specifications & equivalents
The NN4934K is a ISO 15 radial bearing sized 170 x 230 x 60 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 170 mm |
| Outer diameter D | 230 mm |
| Width B | 60 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 400 kN |
| Basic static load rating C0 | 765 kN |
| Fatigue load limit Pu | 75.5 kN |
| Limiting speed (mechanical) | 2500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 6240 g |
| Manufacturer designation | NTN NN4934K |
| 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 | 6.693 in |
|---|---|
| Outer diameter D | 9.055 in |
| Width B | 2.362 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 30 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) | 9 of 18 |
| Bore above smallest NN4900-series size | 70 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN4934K | 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 NN4934K model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NN4934K appears as a 170 mm bore single-row cylindrical roller bearing (400 kN C / 765 kN C0) with a machined or stamped steel cage per the precision execution, listed to the ISO 15 boundary plan. Digit by digit, NN4934K reads as NN (double row, ribbed inner ring, separable outer), ISO 15 series, and bore 170 mm; trailing letters such as EA or E mark the cage/capacity execution and are part of the order number. Line contact between rollers and raceways gives NN4934K high radial capacity but no tolerance for misalignment: beyond roughly 3–4 arc-minutes the roller ends edge-load and fatigue accelerates. Thermal planning around the 2,500 r/min grease ceiling should include the cage type (a machined or stamped steel cage per the precision execution) and oil-flow option to 2,900 r/min for continuously high-duty 170 mm positions. Housing and shaft fillets must clear the ring chamfers of NN4934K; an oversized radius locks the ring on its face and tilts the 60 mm-wide seat.
Typical equipment & failure modes
Common applications
- machine-tool main spindles requiring high radial stiffness
- precision gearbox and indexing-drive shafts
- high-rpm motorised grinding and milling spindles
- CNC lathe and machining-centre spindle radial sets
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- cage distortion after a mounting blow carried through the roller set
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- fretting corrosion on a loose rotating shaft seat
- hard-particle indentation of raceways in unfiltered oil or open arrangements
Selection pitfalls — read before you substitute
- At 170 mm bore, oil-lubricated arrangements toward 2,900 r/min need positive flow and drain design; the 6240 g NN4934K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The K tapered bore of NN4934K is driven up to a measured clearance: skipping the drive-up procedure in favour of a normal press fit leaves the precision spindle set either preloaded hot or loose under load.
- Do not replace NN4934K with a deep-groove ball bearing on rating alone: line contact gives 400 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 K tapered bore of NN4934K is driven up to a measured clearance: skipping the drive-up procedure in favour of a normal press fit leaves the precision spindle set either preloaded hot or loose under load.
- Wide (22/23) and light (10/49) executions at 170 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 400/765 kN ratings, 75.5 kN Pu and 6240 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4934K (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 NN4934K?
NN4934K is an NTN NN double-row precision cylindrical roller bearing to ISO 15: 170 mm bore, 230 mm OD and 60 mm width (6.693 × 9.055 × 2.362 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 400 kN, C0 765 kN, Pu 75.5 kN, grease limiting speed 2,500 r/min, oil 2,900 r/min, mass about 6240 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. NN4934K 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. NN4934K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN4934K?
The K suffix denotes a 1:12 tapered bore. NN4934K 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 NN4934 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NN4934K?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 188.5 mm, Ew 216.5179 mm. The nominal bore/OD remain 170/230 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 2,500 r/min grease / 2,900 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.