NK38-30-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 NK38-30-XL model number is decoded

envelope 38×48×30 mm: 38 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 5.0 mm radial section packed with small-diameter needle rollers C is 43 kN and C0 76 kN at the 38 mm seat; the C/C0 ratio of 0.57 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 48 mm outside diameter the fatigue load limit Cur is 14.3 kN, the limiting speed 12,000 r/min and the thermal reference speed 7,000 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 1.13 kN/mm and per millimetre of width 1.43 kN/mm — the reason 30 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 116 g, just 0.08 g per mm² of projected 48×30 mm envelope, which keeps unbalanced forces low in fast-actuating linkages 38 mm bore marks the medium range: mounting forces and fits become critical, and the 116 g mass calls for proper induction or press tooling rather than hand fitting The hardness requirement is unforgiving: below about 58 HRC the 38 mm journal brinels under the 76 kN static rating, and roughness above raceway finish accelerates roller wear This bearing accepts axial displacement between shaft and housing because the rollers rotate on the free journal; it locates nothing axially and must be flanked by guide faces The -XL suffix is the Schaeffler X-life mark: interchangeable envelope with the basic bearing, but higher load capacity and lower running temperature at the 12,000 r/min limit. Typical applications include agricultural machine pivots and linkages, hydraulic and pneumatic pump eccentrics and textile machine heald and cam shafts, where the 48 mm outside diameter and 43 kN dynamic rating match the duty. In agricultural machine pivots and linkages the unit fits a compact 38 mm seat, and in hydraulic and pneumatic pump eccentrics the 116 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for textile machine heald and cam shafts, relying on the 30 mm width and the published 76 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. On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.

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.
• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.
• 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.