NA4904-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 NA4904-XL model number is decoded

envelope 20×37×17 mm: 20 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 23.7 kN and C0 25.5 kN at the 20 mm seat; the C/C0 ratio of 0.93 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 37 mm outside diameter the fatigue load limit Cur is 4.7 kN, the limiting speed 16,900 r/min and the thermal reference speed 9,400 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 1.19 kN/mm and per millimetre of width 1.39 kN/mm — the reason 17 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 75.2 g, just 0.12 g per mm² of projected 37×17 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 20 mm bore this size balances the 37 mm outside diameter against machineability of the adjacent parts — the most frequently specified band in the HR1 range 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 NA4904-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 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 16,900 r/min limit. Typical applications include copying and printing machine mechanisms, gearbox selector and change linkages and hydraulic and pneumatic pump eccentrics, where the 37 mm outside diameter and 23.7 kN dynamic rating match the duty. In copying and printing machine mechanisms the unit fits a compact 20 mm seat, and in gearbox selector and change linkages the 75.2 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for hydraulic and pneumatic pump eccentrics, relying on the 17 mm width and the published 25.5 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.