NNU4934K bearing: complete specifications & equivalents
The NNU4934K 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 | 6550 g |
| Manufacturer designation | NTN NNU4934K |
| 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 & NNU4900-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 NNU4900-series | 100 mm |
| Largest outer diameter in NNU4900-series | 650 mm |
| Width range across NNU4900-series | 40–170 mm |
| Bore position in NNU4900-series (smallest first) | 9 of 26 |
| Bore above smallest NNU4900-series size | 70 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NNU4934K | 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 NNU4934K model number is decoded
NTN lists NNU4934K on the 170×230 mm envelope, 60 mm wide: a line-contact radial bearing with a machined or stamped steel cage per the precision execution and a grease limiting speed of 2,500 r/min. The leading NNU defines the rib arrangement (double row, ribbed outer ring, separable inner); the dimension-series digits and the two-digit bore code resolve to 170 mm, with 230 mm OD and 60 mm width from the ISO 15 general plan. NTN prints the raceway diameters for this size — Fw 188.5 mm and Ew 216.5179 mm — the envelope inside the 170/230 mm bore/OD where the rollers actually run. Selection arithmetic: Pu 75.5 kN is the fatigue load limit feeding the adjusted-life equation, and the C0/C ratio of 1.91 (765/400 kN) shows the high-static-capacity proportioning of this 170 mm bore. Provide axial location with an adjacent locating bearing rather than expecting the float cylindrical set to hold thrust on the 170 mm shaft.
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
- 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
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- false brinelling on standby machines exposed to external vibration
- brinelling from static overload or impact during handling
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 6550 g NNU4934K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The NNU rib arrangement is not interchangeable with another prefix on the same 170 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 230×60 mm envelope matches.
- The 60 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 170 mm inner ring.
- Wide (22/23) and light (10/49) executions at 170 mm bore share bore but not OD/width; check the full NNU4900 series code before substituting, because housing and shoulder geometry will not interchange.
- The NNU rib arrangement is not interchangeable with another prefix on the same 170 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 230×60 mm envelope matches.
- The 400/765 kN ratings, 75.5 kN Pu and 6550 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4934K (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 NNU4934K?
NNU4934K is an NTN NNU 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 6550 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. NNU4934K is the NNU 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. NNU4934K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NNU bearing like NNU4934K?
The K suffix denotes a 1:12 tapered bore. NNU4934K 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 NNU4934 execution of the same envelope mounts on a plain seat.
What do Fw and Ew mean for NNU4934K?
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.