NKS50-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 NKS50-XL model number is decoded

envelope 50×65×22 mm: 50 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 7.5 mm radial section packed with small-diameter needle rollers C is 48 kN and C0 67 kN at the 50 mm seat; the C/C0 ratio of 0.72 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 65 mm outside diameter the fatigue load limit Cur is 11.8 kN, the limiting speed 8,900 r/min and the thermal reference speed 5,500 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 0.96 kN/mm and per millimetre of width 2.18 kN/mm — the reason 22 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 157 g, just 0.11 g per mm² of projected 65×22 mm envelope, which keeps unbalanced forces low in fast-actuating linkages 50 mm bore marks the medium range: mounting forces and fits become critical, and the 157 g mass calls for proper induction or press tooling rather than hand fitting NKS50-XL has no inner ring: the needle rollers run directly on the shaft journal, so the seat must be hardened (58–64 HRC) and ground to bearing raceway quality As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 11.8 kN Cur value. Typical applications include rocker arms and valve trains, two-stroke and compressor piston pins and small electric motor accessory drives, where the 65 mm outside diameter and 48 kN dynamic rating match the duty. In rocker arms and valve trains the unit fits a compact 50 mm seat, and in two-stroke and compressor piston pins the 157 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for small electric motor accessory drives, relying on the 22 mm width and the published 67 kN static rating. 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. Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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.
• Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations.
• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.