NU 22 Series Cylindrical Roller Bearings

The wide version of the NU 2, and the clearest demonstration that the second field in this designation is a dimension series rather than a diameter series: at every bore the NU 22 has the same outside diameter as the NU 2 and a wider ring — a NU2204 is 20 × 47 × 18 mm against 20 × 47 × 14, and a NU2218 is 90 × 160 × 40 against 90 × 160 × 30. Nothing grows across, so it costs axial room instead of a bigger housing, and the wider rollers are what pay for the extra capacity. Reading it as "22 means bigger across" is the natural mistake, and the outside diameter column is what refutes it.

Wide, not larger — and this is where that is easiest to see. The middle field of NU2204 is the dimension series 22, which carries both digits: 2 for the width series and 2 for the diameter series. The diameter series is the one that sets the outside diameter, and it is 2 on both sides, so the NU 22 and the NU 2 run on the same outside-diameter ladder and the width is the only dimension that moves. Reading "22" as "bigger across" is the natural mistake; the outside diameter column is what refutes it.

Why the NU 22 and the 2200 have the same numbers. The self-aligning 2200 family is the wide version of the light series too, on the same two digits, so the three families line up row for row: NU2204 is 20 × 47 × 18 mm, 2204 is 20 × 47 × 18 mm, and the 1204 that shares their bore is 20 × 47 × 14 mm — same seat, four millimetres less ring. At the top of the series NU2218 is 90 × 160 × 40 mm against the NU218's 90 × 160 × 30 mm.

What the extra width is for. A wider ring means a wider raceway and a longer roller path, so a NU 22 carries more radial load than a NU 2 at the same shaft diameter without asking for a larger housing. That is the trade a width series offers: it spends axial space the designer may already have rather than radial space around the shaft, which is usually the dimension that is actually tight.

Reading the designation. NU2204 is the type code N, the structure letter U, the dimension series 22 and the bore code 04. The type code is written here, unlike in the 2200 self-aligning family where it is dropped — so nothing in a NU2204 has to be inferred from the series. The bore code is the one used throughout: 00, 01, 02 and 03 are 10, 12, 15 and 17 mm, and from 04 upwards the code multiplies by five. NU2204 and NU204 therefore take the same shaft and differ only in how much of it they occupy.

Every designation in the table below links to its own page with the ISO 15 dimensions, the bore-code arithmetic, the radial internal clearance ranges ISO 5753-1 gives for this type, and the same-bore comparison against every other series and type.

This series runs from a 20 mm to a 90 mm bore. The sub-library as a whole reaches 300 mm, and the widest single bearing in it is a 6360, 620 mm across, in the 6300 series. This one stops short of it.

d = bore diameter, D = outside diameter, B = width. All of them are ISO 15 standard values and are the same for every manufacturer. B is the width of a single ring, because the two rings are flush: this type states the same three dimensions a deep groove ball bearing does, with a different bearing inside the same envelope. No chamfer column appears because ISO 15 gives this type a separate chamfer minimum for each ring, and only one of the sources checked here prints both — which is not enough for this library to publish. The last column is derived: radial section = (D − d) / 2, the wall thickness you are working with when you size the housing. No load rating and no limiting speed appears here — see the bearings index for why.

Outside diameter × overall size in millimetres, for the 5 smallest bores in this database. The full charts, one per type, are on the bearings index. Reading a row is what a machine designer does when the shaft is already fixed: the bore does not change, the housing bore does. Across the type boundary the last number changes meaning — it is a width above and a height below — so compare within a type, then decide whether the job wants a ball bearing, a tapered roller or a thrust bearing at all.