NN3068K bearing: complete specifications & equivalents
The NN3068K is a ISO 15 radial bearing sized 340 x 520 x 133 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 340 mm |
| Outer diameter D | 520 mm |
| Width B | 133 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 1800 kN |
| Basic static load rating C0 | 3200 kN |
| Fatigue load limit Pu | 251 kN |
| Limiting speed (mechanical) | 1100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 98500 g |
| Manufacturer designation | NTN NN3068K |
| 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 & NN3000-series range
| Bore d | 13.386 in |
|---|---|
| Outer diameter D | 20.472 in |
| Width B | 5.236 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 90 mm |
| Smallest bore in NN3000-series | 25 mm |
| Largest outer diameter in NN3000-series | 680 mm |
| Width range across NN3000-series | 16–163 mm |
| Bore position in NN3000-series (smallest first) | 34 of 40 |
| Bore above smallest NN3000-series size | 315 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NN3068K | 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 NN3068K model number is decoded
NN3068K is the standard section of the NTN NN3000 dimension series for a 340 mm shaft — 1800 kN of basic dynamic capacity in a 98500 g, open bearing. On the NTN nameplate NN states which ring carries the ribs, which determines whether NN3068K floats or locates; the numeric remainder is the ISO 15 series and 340 mm bore reference, not a fit or clearance instruction. At 1,300 r/min with oil versus 1,100 r/min with grease (a 200 r/min band), lubrication choice for NN3068K is a thermal decision, not just a sealing one. The 5.3 kN-per-mm-bore figure (1800 kN over 340 mm) lets a NN3068K interchange candidate be screened quickly against the same-envelope ball or roller alternatives. After mounting verify the outer ring slides axially by hand at ambient temperature; a stuck float ring in a NN3068K non-locating position preloads the bearing when the shaft grows.
Typical equipment & failure modes
Common applications
- CNC lathe and machining-centre spindle radial sets
- precision rotary-table and dividing-head bearings
- high-speed turbine and turbo-blower rotor supports
- coordinate-measuring and semiconductor-equipment drives
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
- fretting corrosion on a loose rotating shaft seat
Selection pitfalls — read before you substitute
- At 340 mm bore, oil-lubricated arrangements toward 1,300 r/min need positive flow and drain design; the 98500 g NN3068K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 1800/3200 kN pair here belongs to NN3068K as printed, not to the bare size.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 520 mm race brinells and releases as vibration within hours.
- Do not replace NN3068K with a deep-groove ball bearing on rating alone: line contact gives 1800 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
- Grease limiting speed 1,100 r/min and oil 1,300 r/min are different limits for NN3068K: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- The 1800/3200 kN ratings, 251 kN Pu and 98500 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN3068K (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 NN3068K?
NN3068K is an NTN NN double-row precision cylindrical roller bearing to ISO 15: 340 mm bore, 520 mm OD and 133 mm width (13.386 × 20.472 × 5.236 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 1800 kN, C0 3200 kN, Pu 251 kN, grease limiting speed 1,100 r/min, oil 1,300 r/min, mass about 98500 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. NN3068K 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. NN3068K is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN3068K?
The K suffix denotes a 1:12 tapered bore. NN3068K 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 NN3068 execution of the same envelope mounts on a plain seat.
What speeds and lubrication apply to NN3068K?
NTN rates NN3068K at 1,100 r/min with grease and 1,300 r/min with oil. The grease figure is the cage/film mechanical ceiling; the oil figure assumes circulating or carefully supplied oil that removes heat from the line-contact zone.
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.