NKI55-35-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 NKI55-35-XL model number is decoded

envelope 55×72×35 mm: 55 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 8.5 mm radial section packed with small-diameter needle rollers C is 63 kN and C0 130 kN at the 55 mm seat; the C/C0 ratio of 0.48 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 72 mm outside diameter the fatigue load limit Cur is 23.9 kN, the limiting speed 7,700 r/min and the thermal reference speed 4,550 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 1.15 kN/mm and per millimetre of width 1.80 kN/mm — the reason 35 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 379 g, just 0.15 g per mm² of projected 72×35 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 55 mm bore this is a mainstream industrial size — conveyor drives, winches and medium gearboxes use the 35 mm width as a standard mounting space The 8.5 mm section still holds a full needle pack; like all needle bearings it cannot tolerate angular misalignment, so shaft and housing axes must be parallel NKI55/35-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 63 kN C rating and longer nominal life come without an envelope change. Typical applications include small electric motor accessory drives, rocker arms and valve trains and planetary gear bearings, where the 72 mm outside diameter and 63 kN dynamic rating match the duty. In small electric motor accessory drives the unit fits a compact 55 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 130 kN static rating. Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone. 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.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

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