NK68-25 bearing: complete specifications & equivalents
The NK68-25 is a DIN 616 radial bearing sized 68 x 82 x 25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 68 mm |
| Outer diameter D | 82 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 44 kN |
| Basic static load rating C0 | 95 kN |
| Fatigue load limit Pu | 11.8 kN |
| Reference speed (thermal) | 6000 rpm |
| Limiting speed (mechanical) | 6700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 240 g |
| Manufacturer designation | NK 68/25 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & NK-series range
| Bore d | 2.677 in |
|---|---|
| Outer diameter D | 3.228 in |
| Width B | 0.984 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 7 mm |
| Smallest bore in NK-series | 5 mm |
| Largest outer diameter in NK-series | 130 mm |
| Width range across NK-series | 10–40 mm |
| Bore position in NK-series (smallest first) | 36 of 46 |
| Bore above smallest NK-series size | 63 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NK68-25 model number is decoded
Where the shaft can be hardened and ground, SKF offers NK 68/25 in the machined-ring needle roller bearings without inner ring: outer ring only, needle rollers caged between integral flanges, 68 mm bore seat and 82 mm OD. Reading the designation: NK gives the series and the numbers the boundary plan — 68 mm Fw for the shaft seat, 25 mm width; the 82 mm OD comes from the dimension series, and the absence of an inner ring is built into the family name. The machined ring is through-hardened and ground on OD, bore-side raceway and faces; the flanged lip design means the housing shoulder can be omitted — the ring clamps axially between housing wall and cover washer. Selection arithmetic: C 44 kN against C0 95 kN gives a C0/C ratio of 2.16, and the 11.8 kN fatigue load limit Pu sets the floor for the adjusted-life calculation at contaminated lubrication. Fit the outer ring with a press and a fitting sleeve, not by hammering the flanges — rolled flanges chip; the 82 mm ground OD takes the press fit that prevents outer-ring creep in oscillating duty.
Typical equipment & failure modes
Common applications
- crank pins and eccentrics where the hardened journal is the raceway
- gearbox planetary and idler gears on hardened pins
- piston-pin style pivots in hydraulic pumps
- guide rollers running on hardened tracks
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- polymer cage deformation when the local temperature exceeds the 120 °C sustained limit
- abrasive paste formation from dust ingressing past open ends without effective housing seals
- brinelling of raceways from impact or pressing force transmitted through the rolling elements
- rapid raceway scoring when the shaft journal hardness drops below 58 HRC or the ground finish wears away
Selection pitfalls — read before you substitute
- Above 50 mm bore, thermal growth matters: the 68 mm inner ring or journal grows with temperature faster than the housing, and the small clearance of a needle roller contact leaves little reserve — check running clearance hot, not just at assembly.
- Reference and limiting speeds are different limits: the 6,000 r/min reference is the thermal criterion under load, The limiting value is mechanical; the reference value is thermal under load, and grease choice moves it substantially.
- Hardness is load capacity: in families without an inner ring the 68 mm journal must hold 58–64 HRC with a ground finish; a surface that looks fine but sits at 45 HRC will rib the raceway within weeks.
- The 44/95 kN ratings and 240 g mass are SKF catalogue values transcribed from ch. 7.3 of PUB BU/P1 17000 (PDF table page 632); combined-type axial ratings appear in the text above because the structured record carries radial values only.
Frequently asked questions
What mounting mistakes ruin a NK 68/25?
Press on the ring faces only with a fitting sleeve, keep everything square to the 68 mm seat, and never transmit force through the rolling elements. Follow the catalogue's seat tolerances — the narrow needle contact forgives neither tilt nor burrs.
Is the NK 68/25 sealed?
No — this execution is open and depends on the housing sealing arrangement; grease it at assembly and keep the relubrication interval short in dirty duty.
Which dimensions does the NK 68/25 have?
A NK 68/25 measures 68 mm bore/Fw × 82 mm outside diameter × 25 mm width (2.677 × 3.228 × 0.984 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 44 kN, static C0 95 kN, fatigue limit Pu 11.8 kN, limiting speed 6,700 r/min, reference speed 6,000 r/min, mass about 240 g.
What does NK 68/25 mean in SKF part numbering?
NK names a machined-ring needle roller bearing without inner ring: the figures give Fw 68 mm and width 25 mm, OD 82 mm comes from the dimension series, and the flanged outer ring retains the caged rollers.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.3 machined rings with flanges, without an inner ring on 2026-09-26. Read our editorial & correction policy.