NKI9-12-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 NKI9-12-XL model number is decoded

envelope 9×19×12 mm: 9 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 5.0 mm radial section packed with small-diameter needle rollers C is 7.2 kN and C0 7.1 kN at the 9 mm seat; the C/C0 ratio of 1.01 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 19 mm outside diameter the fatigue load limit Cur is 1.31 kN, the limiting speed 26,500 r/min and the thermal reference speed 20,200 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 0.80 kN/mm and per millimetre of width 0.60 kN/mm — the reason 12 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 16.6 g, just 0.07 g per mm² of projected 19×12 mm envelope, which keeps unbalanced forces low in fast-actuating linkages 9 mm bore and only 16.6 g: the smallest sizes demand accurate shaft geometry, because the 5.0 mm section leaves no tolerance for a soft or tapered seat The integral inner ring brings the bore to 9 mm inside the 19×12 mm envelope; removing that ring gives the corresponding RNA/NK execution and a larger shaft for the same housing This is the choice for OEM production on soft shafts: machine the 9 mm seat to the recommended tolerance, fit the bearing, and let the inner ring provide the precision raceway As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 1.31 kN Cur value. Typical applications include hydraulic and pneumatic pump eccentrics, copying and printing machine mechanisms and agricultural machine pivots and linkages, where the 19 mm outside diameter and 7.2 kN dynamic rating match the duty. In hydraulic and pneumatic pump eccentrics the unit fits a compact 9 mm seat, and in copying and printing machine mechanisms the 16.6 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for agricultural machine pivots and linkages, relying on the 12 mm width and the published 7.1 kN static rating. Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO. Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO.
• Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.
• 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.