NK17-20-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 NK17-20-XL model number is decoded

envelope 17×25×20 mm: 17 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 4.0 mm radial section packed with small-diameter needle rollers C is 17.1 kN and C0 20.4 kN at the 17 mm seat; the C/C0 ratio of 0.84 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 25 mm outside diameter the fatigue load limit Cur is 3.6 kN, the limiting speed 22,600 r/min and the thermal reference speed 15,000 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 1.01 kN/mm and per millimetre of width 0.86 kN/mm — the reason 20 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 29.8 g, just 0.06 g per mm² of projected 25×20 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 17 mm bore this size balances the 25 mm outside diameter against machineability of the adjacent parts — the most frequently specified band in the HR1 range The hardness requirement is unforgiving: below about 58 HRC the 17 mm journal brinels under the 20.4 kN static rating, and roughness above raceway finish accelerates roller wear As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 3.6 kN Cur value. Typical applications include motorcycle and light-vehicle transmissions, connecting-rod small ends and two-stroke and compressor piston pins, where the 25 mm outside diameter and 17.1 kN dynamic rating match the duty. In motorcycle and light-vehicle transmissions the unit fits a compact 17 mm seat, and in connecting-rod small ends the 29.8 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for two-stroke and compressor piston pins, relying on the 20 mm width and the published 20.4 kN static rating. 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. 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

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