NKI55-35 bearing: complete specifications & equivalents
The NKI55-35 is a DIN 616 radial bearing sized 55 x 72 x 35 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 55 mm |
| Outer diameter D | 72 mm |
| Width B | 35 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | none |
| Basic dynamic load rating C | 55 kN |
| Basic static load rating C0 | 134 kN |
| Fatigue load limit Pu | 17 kN |
| Reference speed (thermal) | 6700 rpm |
| Limiting speed (mechanical) | 7500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 360 g |
| Manufacturer designation | NKI 55/35 |
| Standard | DIN 616 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with 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. 7.4 machined rings with flanges, with 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 & NKI-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 1.378 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 8.5 mm |
| Smallest bore in NKI-series | 5 mm |
| Largest outer diameter in NKI-series | 130 mm |
| Width range across NKI-series | 12–40 mm |
| Bore position in NKI-series (smallest first) | 21 of 30 |
| Bore above smallest NKI-series size | 50 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the NKI55-35 model number is decoded
NKI 55/35 is a machined-ring needle roller bearing with an inner ring: flanged outer ring plus a separate 55 mm bore inner ring, so the shaft seat needs only ordinary tolerance, as tabulated by SKF in SKF catalogue PUB BU/P1 17000. Reading the designation: the letters name the series with inner ring, the numbers the boundary plan — 55 mm bore (d), 35 mm width; the 72 mm OD follows the dimension series, and the inner ring is a separate ground component. Execution notes: the inner ring is ground on bore and raceway, so the shaft seat is a normal k5/j6; the flanged outer ring needs no housing shoulder, and NA 49 2RS executions add seals with a wider outer ring. For life calculation, the 55/134 kN ratings assume raceway geometry supplied by the shaft and housing in families without an inner ring — journal hardness, roundness and finish are part of the bearing, not of the application. Mounting: heat or press the inner ring onto the 55 mm k5 seat (max 120 °C), fit the flanged outer ring into the H7 housing bore, and check the 35 mm assembly for free rotation before applying load.
Typical equipment & failure modes
Common applications
- agricultural implement pivots and cutter heads
- electric motor armature shafts with ground seats
- printing and paper-handling rollers
- gearbox shafts where the journal cannot be hardened on site
Known failure patterns
- needle edge loading and raceway denting when the shaft deflects beyond the compensation range
- cage pocket wear and roller skew after sustained operation with too little radial preload
- grease starvation at the roller ends when relubrication intervals are stretched in dirty duty
- rolling-contact fatigue spalling after the rated L10 life
- inner-ring bore fretting on a loose shaft seat, migrating hard particles into the rolling contact
Selection pitfalls — read before you substitute
- Above 50 mm bore, thermal growth matters: the 55 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.
- The quoted 55/134 kN ratings are SKF catalogue values for this exact execution (NKI 55/35); ratings can be revised without the order number changing, so keep the catalogue version (SKF catalogue PUB BU/P1 17000) with the drawing.
- Oscillating pivots fail differently: rocking through a small angle concentrates wear in the same roller positions — inspect those zones, and consider rotating the assembly's clock position at service intervals.
- The 55/134 kN ratings and 360 g mass are SKF catalogue values transcribed from ch. 7.4 of PUB BU/P1 17000 (PDF table page 642); 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 NKI 55/35?
Mount the inner ring on the 55 mm seat first (induction heat, max 120 °C, or press), then fit the flanged outer ring into the H7 housing bore. Verify free rotation and, for 2RS executions, check the wider outer ring against the housing depth.
Is the NKI 55/35 sealed?
No — the open execution relies on housing seals; 2RS executions of the 49 series add contact seals with a wider outer ring as a separate order number.
Which dimensions does the NKI 55/35 have?
A NKI 55/35 measures 55 mm bore/Fw × 72 mm outside diameter × 35 mm width (2.165 × 2.835 × 1.378 in). From SKF catalogue PUB BU/P1 17000: radial dynamic rating C 55 kN, static C0 134 kN, fatigue limit Pu 17 kN, limiting speed 7,500 r/min, reference speed 6,700 r/min, mass about 360 g.
What does NKI 55/35 mean in SKF part numbering?
The letters mark a machined-ring needle roller bearing with inner ring: 55 mm bore, 35 mm width, 72 mm OD per the series plan. The hardened inner ring is the raceway, so an ordinary k5 shaft seat suffices.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 7.4 machined rings with flanges, with an inner ring on 2026-09-26. Read our editorial & correction policy.