NU306 Single-row Cylindrical Roller Bearing
NU306 is a single-row cylindrical roller bearing, medium series, with a 30 mm bore, a 72 mm outside diameter and a 19 mm width. Those three numbers are ISO 15 standard values, identical for every manufacturer.
Dimensions
All NU 3 Series designations- Designation
- NU306
- Type
- Single-row cylindrical roller bearing — radial
- Series
- NU 3 Series (medium)
- Bore code
- 06 — 30 mm
- Bore d
- 30 mm (1.1811 in)
- outside diameter D
- 72 mm
- width B
- 19 mm — the assembled width
- Radial section
- 21 mm = (D − d) / 2
Nominal values in millimetres as published in ISO 15, the boundary dimension plan this type is tabulated in. This type is not tabulated with a chamfer here: ISO 15 gives a tapered roller two separate values while the catalogues consulted publish only one of them, and the thrust tables contradict each other inside a single table — so no chamfer figure meets this library’s rule of a checkable second source, and none is printed. That is an absence, not a zero. A bearing that has been fitted with shields or seals carries the same dimensions, because none of the suffixes touches the boundary dimension plan.
Reading the designationwhere 30 mm comes from
The designation is four fields: the type code, a structure letter, the dimension series and the bore code — which is why NU306 is written N then U then 3 then 06. The letter records which ring carries the ribs; every series in this library is NU, and NU shares its boundary dimensions with NJ, NUP, N and NF, which differ only in that arrangement. For codes 04 and above the bore is the code multiplied by five, which is why 06 gives 30 mm. The four exceptions are 00, 01, 02 and 03 at 10, 12, 15 and 17 mm.
Position in the series3 of 12 in NU 3 Series
Radial internal clearanceISO 5753-1, bore 24–30 mm
| Group | Radial internal clearance | When it is used |
|---|---|---|
| C2 | 0–25 µm | Tighter than default; for fits that already take up the clearance. |
| CN (normal) | 20–45 µm | The default — usually not marked on the bearing at all. |
| C3 | 35–60 µm | Interference fits, electric motors, hot inner ring. The common upgrade. |
| C4 | 50–75 µm | Heavy interference fits and high-temperature service. |
| C5 | 70–95 µm | The loosest group in the table; special applications. |
Values are the pre-mounting radial internal clearance for a single-row cylindrical roller bearing with a cylindrical bore, in micrometres, from ISO 5753-1. Pressing the inner ring onto a shaft and running the inner ring hotter than the outer ring both close this up — an interference of a few micrometres is a few micrometres straight out of the running clearance, which is the whole reason C3 exists. For this bore, normal (CN) is 20–45 µm and C3 is 35–60 µm.
What is deliberately not publishedwhy there is no load rating here
No load rating, no limiting speed and no mass appears on this page. Those are catalogue values rather than standard values: ISO 281 defines how a dynamic rating is calculated, not what it comes out as, and the result depends on internal geometry — ball or roller diameter, the complement, raceway conformity — that none of the boundary dimension plans (ISO 15, ISO 355, ISO 104) fixes. Published catalogue figures for one and the same designation differ between makes by several percent at these sizes, and limiting speed additionally depends on lubrication and on whether the bearing is open, shielded or sealed. Publishing any single figure here would dress a catalogue entry up as a property of the designation. Take the rating from the catalogue of the bearing you actually buy.
The dimensions above are a different matter, and they are the reason a designation is worth anything: the boundary dimensions — bore, outside diameter and the section dimensions of the plan this type is tabulated in, plus the chamfer minimum where that plan gives one — are fixed by the standard, so every maker's bearing of this designation fits the same shaft and the same housing.
Same bore, every series and typewhat a 30 mm shaft would take instead
| Designation | Series | Type | D | Overall size (B / T / H) | Section (D − d)/2 | vs NU306 |
|---|---|---|---|---|---|---|
| NU306 | Medium — this bearing | Cylindrical roller | 72 | 19 B | 21 | — |
| 61706 | 61700 Series — Extra-thin | Deep groove ball | 37 | 4 B | 3.5 | -35 mm on D |
| 61806 | 61800 Series — Ultra-thin | Deep groove ball | 42 | 7 B | 6 | -30 mm on D |
| 61906 | 61900 Series — Thin | Deep groove ball | 47 | 9 B | 8.5 | -25 mm on D |
| 51106 | 51100 Series — Light | Thrust ball | 47 | 11 H | 8.5 | -25 mm on D |
| 51206 | 51200 Series — Medium | Thrust ball | 52 | 16 H | 11 | -20 mm on D |
| 6006 | 6000 Series — Extra-light | Deep groove ball | 55 | 13 B | 12.5 | -17 mm on D |
| 16006 | 16000 Series — Narrow | Deep groove ball | 55 | 9 B | 12.5 | -17 mm on D |
| 6206 | 6200 Series — Light | Deep groove ball | 62 | 16 B | 16 | -10 mm on D |
| 1206 | 1200 Series — Light | Self-aligning ball | 62 | 16 B | 16 | -10 mm on D |
| 2206 | 2200 Series — Light, wide | Self-aligning ball | 62 | 20 B | 16 | -10 mm on D |
| 30206 | 30200 Series — Light | Tapered roller | 62 | 17.25 T | 16 | -10 mm on D |
| NU206 | NU 2 Series — Light | Cylindrical roller | 62 | 16 B | 16 | -10 mm on D |
| NU2206 | NU 22 Series — Wide light | Cylindrical roller | 62 | 20 B | 16 | -10 mm on D |
| 6306 | 6300 Series — Medium | Deep groove ball | 72 | 19 B | 21 | 0 mm on D |
| 1306 | 1300 Series — Medium | Self-aligning ball | 72 | 19 B | 21 | 0 mm on D |
| 2306 | 2300 Series — Medium, wide | Self-aligning ball | 72 | 27 B | 21 | 0 mm on D |
| 30306 | 30300 Series — Medium | Tapered roller | 72 | 20.75 T | 21 | 0 mm on D |
| NU2306 | NU 23 Series — Wide medium | Cylindrical roller | 72 | 27 B | 21 | 0 mm on D |
| 6406 | 6400 Series — Heavy | Deep groove ball | 90 | 23 B | 30 | +18 mm on D |
20 series across five bearing types, one bore: the shaft diameter is the same in every row, so the only thing that changes is what the housing and the axial space have to accommodate. Outside diameter and the overall size are standard boundary dimensions in the plan each type is tabulated in (ISO 15 / ISO 15 / ISO 355 / ISO 104 / ISO 15) — the same figure for every manufacturer. The section column is derived as (D − d) / 2. Load capacity rises with the outside diameter, but the figure itself has to come from the manufacturer’s catalogue for the bearing you actually buy — see above.