NK28-20-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 NK28-20-XL model number is decoded

envelope 28×37×20 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 24.8 kN and C0 34 kN at the 28 mm seat; the C/C0 ratio of 0.73 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 6 kN, the limiting speed 15,800 r/min and the thermal reference speed 9,300 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 0.89 kN/mm and per millimetre of width 1.24 kN/mm — the reason 20 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 52.2 g, just 0.07 g per mm² of projected 37×20 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 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 Omitting the inner ring frees radial space — at a 28 mm shaft the outer diameter is only 37 mm and the width 20 mm, yet C is 24.8 kN -XL means this is an X-life bearing — Schaeffler's upgraded performance level with smoother raceways, so the 24.8 kN C rating and longer nominal life come without an envelope change. Typical applications include two-stroke and compressor piston pins, motorcycle and light-vehicle transmissions and rocker arms and valve trains, where the 37 mm outside diameter and 24.8 kN dynamic rating match the duty. In two-stroke and compressor piston pins the unit fits a compact 28 mm seat, and in motorcycle and light-vehicle transmissions the 52.2 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for rocker arms and valve trains, relying on the 20 mm width and the published 34 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.
• Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO.