SKFNU-228-ECMLSingle-Row Cylindrical Roller Bearing 140 x 250 x 42 mm, NU Design, Straight Bore, Machined Brass Window Cage, Non-Locating

Product Description

What this part is

An SKF NU 228 ECML single-row cylindrical roller bearing, 140 mm bore x 250 mm outside diameter x 42 mm wide, straight bore, with a machined brass window-type cage and SKF’s increased-capacity E internal design. One row of cylindrical rollers carries 510 kN static radial load at speeds to 3 200 rpm in a 55 mm cross-section. This is a heavy industrial bearing for gearboxes, electric motors and rolling mill drives.

Decoding the designation

NU — single row with two integral flanges on the outer ring and a plain, flangeless inner ring. The bearing accommodates axial displacement in both directions.
2 — ISO dimension series 2 (medium section).
28 — 140 mm bore.
E — SKF increased load capacity design: a larger and fuller roller complement than the original NU228.
C — modified internal design, the optimised roller and raceway geometry that goes with the E series.
M — machined brass cage.
L — cage guided on a ring rather than on the rollers.

Axial location and the NU, N, NJ and NUP designs:
Flange arrangement is the specification a cylindrical roller bearing is selected on, and the four designs are not interchangeable:

NU — two outer-ring flanges, plain inner ring. Non-locating: the rollers run axially along the inner raceway, so the shaft moves axially through the bearing. This bearing.
N — two inner-ring flanges, plain outer ring. Also non-locating, with the flanges on the opposite ring.
NJ — one inner-ring flange. Locates the shaft in one direction.
NUP — two inner-ring flanges, one a loose flange ring. Locates the shaft in both directions.

An NU228 in place of an NJ228 or NUP228 removes axial location from that position, and an NJ228 or NUP228 in place of this NU228 adds axial constraint the arrangement did not allow for. All four share the 140 x 250 x 42 mm envelope, so the flange arrangement is the specification that decides fit.

What these specs mean in practice

Line contact between roller and raceway is what buys the load capacity: a cylindrical roller spreads its load along a line rather than a point, giving several times the radial rating of a ball bearing in the same envelope, at the cost of a lower speed ceiling and no meaningful thrust capacity. The E design raises that capacity again by fitting a larger roller set into the same boundary dimensions.

A machined brass window cage suits heavy loads, shock loading, high temperature and oil lubrication, and it tolerates conditions that would break down a polyamide cage. Ring guidance keeps the cage stable at speed rather than letting it ride on the rollers, which is what supports the 3 200 rpm ceiling on a bearing of this size and mass. Because the plain inner ring separates from the roller and cage assembly, the two halves mount independently — useful where the shaft and housing are assembled apart from each other.

Published ratings and mounting data

Bore d: 140 mm (5.5118 in) — Outside diameter D: 250 mm (9.8425 in) — Width B: 42 mm (1.6535 in)
Basic static load rating C0: 510 kN
Limiting speed: 3 200 rpm
Rows: 1 — rolling element: cylindrical roller
Bore form: straight cylindrical
Flange arrangement: two outer-ring flanges, plain inner ring (NU)
Cage: machined brass, window type, ring-guided
Internal design: SKF E, increased load capacity
Radial internal clearance: normal (CN) — no clearance suffix in the designation
Closure: open, no seals or shields
Material: through-hardened bearing steel
Separable: the plain inner ring lifts away from the outer ring, roller and cage assembly

Quantity and configuration

Sold as 1 Pc — one complete bearing: the twin-flanged outer ring with its roller and brass cage assembly, and the plain inner ring. The two halves are a matched set.

Fitting notes

The plain inner ring goes on with an interference fit, heated or pressed square to the shaft shoulder, and the outer ring with its roller set seats in the housing bore to the fit the drawing calls for. The halves mount independently and the roller assembly is introduced over the inner ring afterwards, squarely and without cocking the rollers over the ring corner. Each ring is marked, and the roller assembly returns to its original outer ring. A brass cage of this size takes oil or grease relubrication on a schedule set by the running temperature.

Interchange guidance

Same-specification equivalents at 140 x 250 x 42 mm with the NU flange arrangement and a machined brass cage: FAG NU228-E-XL-M1, NSK NU228EM, NTN NU228EM, Koyo NU228M, Nachi NU228EM, Timken NU228EMA. Related sizes, not substitutes: N228, NJ228 and NUP228 share this envelope but carry their flanges differently and behave differently axially; NU 228 ECP is the same bearing with a polyamide cage and a lower temperature ceiling; NU 228 ECML/C3 is the same bearing with greater-than-normal clearance and a different fit-up; the original non-E NU228 has a lower load rating; and the double-row NN3028 mounts entirely differently.