NKIS55-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 NKIS55-XL model number is decoded

envelope 55×85×28 mm: 55 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 15.0 mm radial section packed with small-diameter needle rollers C is 75 kN and C0 108 kN at the 55 mm seat; the C/C0 ratio of 0.69 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 85 mm outside diameter the fatigue load limit Cur is 19.4 kN, the limiting speed 6,900 r/min and the thermal reference speed 4,000 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 1.36 kN/mm and per millimetre of width 2.68 kN/mm — the reason 28 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 558 g, just 0.23 g per mm² of projected 85×28 mm envelope, which keeps unbalanced forces low in fast-actuating linkages 55 mm bore marks the medium range: mounting forces and fits become critical, and the 558 g mass calls for proper induction or press tooling rather than hand fitting This is the choice for OEM production on soft shafts: machine the 55 mm seat to the recommended tolerance, fit the bearing, and let the inner ring provide the precision raceway NKIS55-XL is supplied with a machined inner ring, so it mounts on an ordinary turned and ground shaft of normal tolerance — hardening the journal is not required -XL means this is an X-life bearing — Schaeffler's upgraded performance level with smoother raceways, so the 75 kN C rating and longer nominal life come without an envelope change. Typical applications include hydraulic and pneumatic pump eccentrics, copying and printing machine mechanisms and agricultural machine pivots and linkages, where the 85 mm outside diameter and 75 kN dynamic rating match the duty. In hydraulic and pneumatic pump eccentrics the unit fits a compact 55 mm seat, and in copying and printing machine mechanisms the 558 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for agricultural machine pivots and linkages, relying on the 28 mm width and the published 108 kN static rating. 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. Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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.
• Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.
• Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations.