NKI50-35-XL bearing: complete specifications & equivalents

Specification table

Source: catalog reference (HR1 2026-09-25) · extracted 2026-09-30

Parameters extracted from the official FAG Rolling Bearings catalogue (HR1 2026-09-25); FAG® is a trademark of Schaeffler Technologies AG & Co. KG, used here for identification only — mpnbase is not an authorized FAG/Schaeffler distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at schaeffler.com.

Cross references & equivalents

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 NKI50-35-XL model number is decoded

envelope 50×68×35 mm: 50 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 9.0 mm radial section packed with small-diameter needle rollers C is 60 kN and C0 118 kN at the 50 mm seat; the C/C0 ratio of 0.51 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 68 mm outside diameter the fatigue load limit Cur is 21.6 kN, the limiting speed 8,400 r/min and the thermal reference speed 4,900 r/min; for small needle bearings the reference speed can exceed the kinematic limit, so the lower of the two governs the application dynamic capacity per millimetre of bore is 1.20 kN/mm and per millimetre of width 1.71 kN/mm — the reason 35 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 379 g, just 0.16 g per mm² of projected 68×35 mm envelope, which keeps unbalanced forces low in fast-actuating linkages the 50 mm bore places this bearing in the medium band, where the 68 mm envelope already carries ratings in the tens of kilonewtons Cur 21.6 kN, limiting speed 8,400 r/min, reference speed 4,900 r/min — the inner ring adds a few grams (total 379 g) but removes the hardening requirement The inner ring is separable, so the outer-ring/roller assembly can be pressed into the housing first; the 118 kN C0 rating still assumes full rigid support under both rings The -XL suffix marks the X-life execution: refined raceway topography and upgraded materials lift the basic ratings versus the non-X-life bearing at the same 50×68×35 mm envelope. Typical applications include small electric motor accessory drives, rocker arms and valve trains and planetary gear bearings, where the 68 mm outside diameter and 60 kN dynamic rating match the duty. In small electric motor accessory drives the unit fits a compact 50 mm seat, and in rocker arms and valve trains the 379 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for planetary gear bearings, relying on the 35 mm width and the published 118 kN static rating. On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions. Do not press an RNA/NK assembly in through the outer ring when mounting it on a shaft, and vice versa — rolling forces through the wrong ring bruises the raceways.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.
• Do not press an RNA/NK assembly in through the outer ring when mounting it on a shaft, and vice versa — rolling forces through the wrong ring bruises the raceways.
• Adding an IR inner ring changes the envelope logic: the same outer assembly then fits a smaller shaft — recheck bore, clearance and ratings when substituting.