30311 Single-row Tapered Roller Bearing
30311 is a single-row tapered roller bearing, medium series, with a 55 mm bore, a 120 mm outside diameter, a 31.5 mm total width, a 29 mm inner ring width and a 25 mm outer ring width. Those five numbers are ISO 355 standard values, identical for every manufacturer.
Dimensions
All 30300 Series designations- Designation
- 30311
- Type
- Single-row tapered roller bearing — radial
- Series
- 30300 Series (medium)
- Bore code
- 11 — 55 mm
- Bore d
- 55 mm (2.1654 in)
- outside diameter D
- 120 mm
- total width T
- 31.5 mm — the assembled width
- inner ring width B
- 29 mm
- outer ring width C
- 25 mm
- Radial section
- 32.5 mm = (D − d) / 2
Nominal values in millimetres as published in ISO 355, the boundary dimension plan this type is tabulated in. This type is not tabulated with a chamfer here: ISO 355 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 55 mm comes from
The designation is three fields: type, the series and the bore code. For codes 04 and above the bore is the code multiplied by five, which is why 11 gives 55 mm. The four exceptions are 00, 01, 02 and 03 at 10, 12, 15 and 17 mm.
Position in the series10 of 19 in 30300 Series
No radial clearance table on this pagesingle-row tapered roller bearing
A tapered roller bearing is not given a radial clearance group. Its running clearance is set axially when the bearing is mounted — by the position of the cone relative to the cup, or by a locknut on the shaft — and it is measured as an end float in millimetres rather than as a radial figure in micrometres. ISO 5753-1, the table used everywhere else in this sub-library, is the radial table for radial bearings with a cylindrical bore; it is not the right document for this designation, so a table from it would be answering a question this bearing does not have.
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 55 mm shaft would take instead
| Designation | Series | Type | D | Overall size (B / T / H) | Section (D − d)/2 | vs 30311 |
|---|---|---|---|---|---|---|
| 30311 | Medium — this bearing | Tapered roller | 120 | 31.5 T | 32.5 | — |
| 61711 | 61700 Series — Extra-thin | Deep groove ball | 68 | 7 B | 6.5 | -52 mm on D |
| 61811 | 61800 Series — Ultra-thin | Deep groove ball | 72 | 9 B | 8.5 | -48 mm on D |
| 51111 | 51100 Series — Light | Thrust ball | 78 | 16 H | 11.5 | -42 mm on D |
| 61911 | 61900 Series — Thin | Deep groove ball | 80 | 13 B | 12.5 | -40 mm on D |
| 6011 | 6000 Series — Extra-light | Deep groove ball | 90 | 18 B | 17.5 | -30 mm on D |
| 16011 | 16000 Series — Narrow | Deep groove ball | 90 | 11 B | 17.5 | -30 mm on D |
| 51211 | 51200 Series — Medium | Thrust ball | 90 | 25 H | 17.5 | -30 mm on D |
| 6211 | 6200 Series — Light | Deep groove ball | 100 | 21 B | 22.5 | -20 mm on D |
| 30211 | 30200 Series — Light | Tapered roller | 100 | 22.75 T | 22.5 | -20 mm on D |
| 6311 | 6300 Series — Medium | Deep groove ball | 120 | 29 B | 32.5 | 0 mm on D |
| 6411 | 6400 Series — Heavy | Deep groove ball | 140 | 33 B | 42.5 | +20 mm on D |
12 series across three 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 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.