NKI38-20-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 NKI38-20-XL model number is decoded

envelope 38×53×20 mm: 38 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 30.5 kN and C0 51 kN at the 38 mm seat; the C/C0 ratio of 0.60 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 53 mm outside diameter the fatigue load limit Cur is 9.1 kN, the limiting speed 10,700 r/min and the thermal reference speed 6,000 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 0.80 kN/mm and per millimetre of width 1.52 kN/mm — the reason 20 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 136 g, just 0.13 g per mm² of projected 53×20 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 38 mm bore this is a mainstream industrial size — conveyor drives, winches and medium gearboxes use the 20 mm width as a standard mounting space Reading the NKI prefix: machined-ring needle bearing with inner ring, one roller row, capable of pure radial load at 30.5 kN C NKI38/20-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 As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 9.1 kN Cur value. Typical applications include copying and printing machine mechanisms, gearbox selector and change linkages and hydraulic and pneumatic pump eccentrics, where the 53 mm outside diameter and 30.5 kN dynamic rating match the duty. In copying and printing machine mechanisms the unit fits a compact 38 mm seat, and in gearbox selector and change linkages the 136 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for hydraulic and pneumatic pump eccentrics, relying on the 20 mm width and the published 51 kN static rating. Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately. 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

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