NKS37-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 NKS37-XL model number is decoded

envelope 37×52×22 mm: 37 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 7.5 mm radial section packed with small-diameter needle rollers C is 41.5 kN and C0 50 kN at the 37 mm seat; the C/C0 ratio of 0.83 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 52 mm outside diameter the fatigue load limit Cur is 8.8 kN, the limiting speed 11,700 r/min and the thermal reference speed 7,100 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 1.12 kN/mm and per millimetre of width 1.89 kN/mm — the reason 22 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 123 g, just 0.11 g per mm² of projected 52×22 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 37 mm bore this is a mainstream industrial size — conveyor drives, winches and medium gearboxes use the 22 mm width as a standard mounting space NKS37-XL has no inner ring: the needle rollers run directly on the shaft journal, so the seat must be hardened (58–64 HRC) and ground to bearing raceway quality The thin 7.5 mm section makes the 123 g bearing sensitive to seat geometry — a tapered or lobed journal preloads part of the needle set and shows up as local pitting -XL means this is an X-life bearing — Schaeffler's upgraded performance level with smoother raceways, so the 41.5 kN C rating and longer nominal life come without an envelope change. Typical applications include rocker arms and valve trains, two-stroke and compressor piston pins and small electric motor accessory drives, where the 52 mm outside diameter and 41.5 kN dynamic rating match the duty. In rocker arms and valve trains the unit fits a compact 37 mm seat, and in two-stroke and compressor piston pins the 123 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for small electric motor accessory drives, relying on the 22 mm width and the published 50 kN static rating. On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions. 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

• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.
• Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations.
• 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.