NKI40-30-TW-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 NKI40-30-TW-XL model number is decoded

envelope 40×55×30 mm: 40 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 7.5 mm radial section packed with small-diameter needle rollers C is 54 kN and C0 97 kN at the 40 mm seat; the C/C0 ratio of 0.56 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 55 mm outside diameter the fatigue load limit Cur is 18.6 kN, the limiting speed 10,200 r/min and the thermal reference speed 5,900 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 1.35 kN/mm and per millimetre of width 1.80 kN/mm — the reason 30 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 216 g, just 0.13 g per mm² of projected 55×30 mm envelope, which keeps unbalanced forces low in fast-actuating linkages the 40 mm bore places this bearing in the medium band, where the 55 mm envelope already carries ratings in the tens of kilonewtons NKI40/30-TW-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 Reading the NKI prefix: machined-ring needle bearing with inner ring, one roller row, capable of pure radial load at 54 kN C As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 18.6 kN Cur value. Typical applications include copying and printing machine mechanisms, gearbox selector and change linkages and hydraulic and pneumatic pump eccentrics, where the 55 mm outside diameter and 54 kN dynamic rating match the duty. In copying and printing machine mechanisms the unit fits a compact 40 mm seat, and in gearbox selector and change linkages the 216 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for hydraulic and pneumatic pump eccentrics, relying on the 30 mm width and the published 97 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. 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

• 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.
• Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.