NN3068 bearing: complete specifications & equivalents
The NN3068 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 | 102000 g |
| Manufacturer designation | NTN NN3068 |
| 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 | 68 |
| 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 |
|---|---|---|---|
| NN3068 | 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 NN3068 model number is decoded
The NTN order number NN3068 denotes a 340×520×133 mm (13.386 × 20.472 × 5.236 in) cylindrical roller bearing in the NN3000 family, a machined or stamped steel cage per the precision execution. On the NTN nameplate NN states which ring carries the ribs, which determines whether NN3068 floats or locates; the numeric remainder is the ISO 15 series and 340 mm bore reference, not a fit or clearance instruction. Line contact between rollers and raceways gives NN3068 high radial capacity but no tolerance for misalignment: beyond roughly 3–4 arc-minutes the roller ends edge-load and fatigue accelerates. Selection arithmetic: Pu 251 kN is the fatigue load limit feeding the adjusted-life equation, and the C0/C ratio of 1.78 (3200/1800 kN) shows the high-static-capacity proportioning of this 340 mm bore. Heat the inner ring to max 120 °C for the 340 mm interference fit and support the ring face square during fitting; cocking over a keyway brinells the raceway before first rotation.
Typical equipment & failure modes
Common applications
- precision rotary-table and dividing-head bearings
- high-speed turbine and turbo-blower rotor supports
- coordinate-measuring and semiconductor-equipment drives
- machine-tool main spindles requiring high radial stiffness
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- 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
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
- rolling-contact fatigue after the catalogue L10 life is exceeded
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 102000 g NN3068 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- Open NN3068 units need application-supplied sealing and a defined lubricant schedule; film thickness is the first failure mode for line contact when viscosity drops at the 340 mm contact.
- 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.
- Grease limiting speed 1,100 r/min and oil 1,300 r/min are different limits for NN3068: the first is the cage/lubricant mechanical ceiling, the second assumes real oil flow rather than an oil bath.
- Wide (22/23) and light (10/49) executions at 340 mm bore share bore but not OD/width; check the full NN3000 series code before substituting, because housing and shoulder geometry will not interchange.
- The 1800/3200 kN ratings, 251 kN Pu and 102000 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN3068 (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 NN3068?
NN3068 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 102000 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. NN3068 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. NN3068 is supplied in the standard open execution shown in the table.
What does the K tapered bore mean on a precision NN bearing like NN3068?
NN3068 has a cylindrical bore and mounts on a plain machined shaft seat; a K execution (1:12 taper) exists in the NN3000 series when preload must be set by drive-up on a tapered seat.
What speeds and lubrication apply to NN3068?
NTN rates NN3068 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.