NKS25-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 NKS25-XL model number is decoded

envelope 25×38×20 mm: 25 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 6.5 mm radial section packed with small-diameter needle rollers C is 31 kN and C0 33.5 kN at the 25 mm seat; the C/C0 ratio of 0.93 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 38 mm outside diameter the fatigue load limit Cur is 5.9 kN, the limiting speed 16,600 r/min and the thermal reference speed 9,700 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 1.24 kN/mm and per millimetre of width 1.55 kN/mm — the reason 20 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 68.1 g, just 0.09 g per mm² of projected 38×20 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 25 mm bore this size balances the 38 mm outside diameter against machineability of the adjacent parts — the most frequently specified band in the HR1 range The thin 6.5 mm section makes the 68.1 g bearing sensitive to seat geometry — a tapered or lobed journal preloads part of the needle set and shows up as local pitting The hardness requirement is unforgiving: below about 58 HRC the 25 mm journal brinels under the 33.5 kN static rating, and roughness above raceway finish accelerates roller wear X-life status (-XL) indicates the current Schaeffler premium execution at 25 mm bore; the 33.5 kN C0 rating reflects the improved rolling-contact geometry. Typical applications include textile machine heald and cam shafts, agricultural machine pivots and linkages and connecting-rod small ends, where the 38 mm outside diameter and 31 kN dynamic rating match the duty. In textile machine heald and cam shafts the unit fits a compact 25 mm seat, and in agricultural machine pivots and linkages the 68.1 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for connecting-rod small ends, relying on the 20 mm width and the published 33.5 kN static rating. Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO. 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

• Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO.
• 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.
• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.