NK28-30-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 NK28-30-XL model number is decoded

envelope 28×37×30 mm: 28 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 4.5 mm radial section packed with small-diameter needle rollers C is 37 kN and C0 57 kN at the 28 mm seat; the C/C0 ratio of 0.65 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 10.7 kN, the limiting speed 15,800 r/min and the thermal reference speed 9,000 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 1.32 kN/mm and per millimetre of width 1.23 kN/mm — the reason 30 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 82 g, just 0.07 g per mm² of projected 37×30 mm envelope, which keeps unbalanced forces low in fast-actuating linkages the 28 mm bore falls in the small band, the workhorse size for gearbox planetary positions, hydraulic pumps and general cam and linkage duty The thin 4.5 mm section makes the 82 g bearing sensitive to seat geometry — a tapered or lobed journal preloads part of the needle set and shows up as local pitting This bearing accepts axial displacement between shaft and housing because the rollers rotate on the free journal; it locates nothing axially and must be flanked by guide faces 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 28×37×30 mm envelope. 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 37 kN dynamic rating match the duty. In copying and printing machine mechanisms the unit fits a compact 28 mm seat, and in gearbox selector and change linkages the 82 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for hydraulic and pneumatic pump eccentrics, relying on the 30 mm width and the published 57 kN static rating. Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately. 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

• Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.
• 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.
• 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.