2306 Double-row Self-aligning Ball Bearing
2306 is a double-row self-aligning ball bearing, medium, wide series, with a 30 mm bore, a 72 mm outside diameter and a 27 mm width. Those numbers — the bore, outside diameter, width and the 1.1 mm minimum chamfer — are ISO 15 standard values, identical for every manufacturer.
Dimensions
All 2300 Series designations- Designation
- 2306
- Type
- Double-row self-aligning ball bearing — radial
- Bore code
- 06 — 30 mm
- Bore d
- 30 mm (1.1811 in)
- outside diameter D
- 72 mm
- width B
- 27 mm — the assembled width
- Chamfer, r s min
- 1.1 mm — minimum, not nominal
- 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. The chamfer figure is the minimum single chamfer dimension the plan gives (r s min); the matching maximum is in ISO 582 — which is why the row says “min” and not an equality. 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
This one is not assembled the way the rest of this library assembles a designation — 2306 is written 23 followed by the bore code. The bore code still reads exactly as it does elsewhere — the four exceptions are 00, 01, 02 and 03 at 10, 12, 15 and 17 mm, and from 04 upwards the code is multiplied by five, which is why 06 gives 30 mm.
Position in the series7 of 21 in 2300 Series
No radial clearance table on this pagedouble-row self-aligning ball bearing
A self-aligning ball bearing does have radial internal clearance ranges of its own: ISO 5753-1 tabulates them for this type on a table of its own. That table is not reproduced here. The clearance table used elsewhere in this sub-library was taken from the radial-contact groove ball section of the same standard, and its figures are not this bearing’s — the bore of a 23-series bearing falls inside the span it covers, so a row can be looked up, but it would be a correct number under a wrong heading.
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 2306 |
|---|---|---|---|---|---|---|
| 2306 | Medium, wide — this bearing | Self-aligning ball | 72 | 27 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 |
| 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 |
| 30306 | 30300 Series — Medium | Tapered roller | 72 | 20.75 T | 21 | 0 mm on D |
| 6406 | 6400 Series — Heavy | Deep groove ball | 90 | 23 B | 30 | +18 mm on D |
16 series across four 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) — 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.