NK37-20-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 NK37-20-XL model number is decoded

envelope 37×47×20 mm: 37 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 28 kN and C0 43.5 kN at the 37 mm seat; the C/C0 ratio of 0.64 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 47 mm outside diameter the fatigue load limit Cur is 7.8 kN, the limiting speed 12,300 r/min and the thermal reference speed 7,400 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 0.76 kN/mm and per millimetre of width 1.40 kN/mm — the reason 20 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 77 g, just 0.08 g per mm² of projected 47×20 mm envelope, which keeps unbalanced forces low in fast-actuating linkages the 37 mm bore places this bearing in the medium band, where the 47 mm envelope already carries ratings in the tens of kilonewtons The hardness requirement is unforgiving: below about 58 HRC the 37 mm journal brinels under the 43.5 kN static rating, and roughness above raceway finish accelerates roller wear Reading the NK prefix: a machined (not drawn-cup) outer ring with the needle complement; an inner ring from the IR series can be added later if the shaft cannot be hardened The -XL suffix marks the X-life execution: refined raceway topography and upgraded materials lift the basic ratings versus the non-X-life bearing at the same 37×47×20 mm envelope. Typical applications include gearbox selector and change linkages, planetary gear bearings and copying and printing machine mechanisms, where the 47 mm outside diameter and 28 kN dynamic rating match the duty. In gearbox selector and change linkages the unit fits a compact 37 mm seat, and in planetary gear bearings the 77 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for copying and printing machine mechanisms, relying on the 20 mm width and the published 43.5 kN static rating. On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions. Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.

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.
• Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.
• Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.