NA4908 Single-row Needle Roller Bearing With Machined Rings
NA4908 is a single-row needle roller bearing with machined rings, light series, with a 40 mm bore, a 48 mm needle complement diameter, a 62 mm outside diameter and a 22 mm width. Those numbers — the bore, needle complement diameter, outside diameter, width and the 0.6 mm minimum chamfer — are ISO 1206 standard values, identical for every manufacturer.
Dimensions
All NA 49 Series designations- Designation
- NA4908
- Type
- Single-row needle roller bearing with machined rings — radial
- Series
- NA 49 Series (light)
- Bore code
- 08 — 40 mm
- Bore d
- 40 mm (1.5748 in)
- needle complement diameter Fw
- 48 mm
- outside diameter D
- 62 mm
- width B
- 22 mm — the assembled width
- Chamfer, r s min
- 0.6 mm — minimum, not nominal
- Radial section
- 11 mm = (D − d) / 2
Nominal values in millimetres as published in ISO 1206, 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 40 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 08 gives 40 mm. The four exceptions are 00, 01, 02 and 03 at 10, 12, 15 and 17 mm.
Position in the series12 of 28 in NA 49 Series
No radial clearance table on this pagesingle-row needle roller bearing with machined rings
ISO 5753-1 does give needle roller bearings a radial clearance table of their own, and the bore of a na49-series bearing falls inside it. What stops a table appearing here is not the standard but the reproductions of it: the catalogue versions consulted contradict each other in every clearance group, so none of them can be confirmed as the standard’s own, and this library does not publish a figure it cannot attribute. That is the opposite of the tapered and thrust cases above — there the standard fixes a different quantity, here the quantity is fixed and the figures differ.
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, ISO 1206) 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 40 mm shaft would take instead
| Designation | Series | Type | D | Overall size (B / T / H) | Section (D − d)/2 | vs NA4908 |
|---|---|---|---|---|---|---|
| NA4908 | Light — this bearing | Needle roller | 62 | 22 B | 11 | — |
| 61708 | 61700 Series — Extra-thin | Deep groove ball | 50 | 6 B | 5 | -12 mm on D |
| 61808 | 61800 Series — Ultra-thin | Deep groove ball | 52 | 7 B | 6 | -10 mm on D |
| 51108 | 51100 Series — Light | Thrust ball | 60 | 13 H | 10 | -2 mm on D |
| 61908 | 61900 Series — Thin | Deep groove ball | 62 | 12 B | 11 | 0 mm on D |
| 6008 | 6000 Series — Extra-light | Deep groove ball | 68 | 15 B | 14 | +6 mm on D |
| 16008 | 16000 Series — Narrow | Deep groove ball | 68 | 9 B | 14 | +6 mm on D |
| 51208 | 51200 Series — Medium | Thrust ball | 68 | 19 H | 14 | +6 mm on D |
| 6208 | 6200 Series — Light | Deep groove ball | 80 | 18 B | 20 | +18 mm on D |
| 1208 | 1200 Series — Light | Self-aligning ball | 80 | 18 B | 20 | +18 mm on D |
| 2208 | 2200 Series — Light, wide | Self-aligning ball | 80 | 23 B | 20 | +18 mm on D |
| 30208 | 30200 Series — Light | Tapered roller | 80 | 19.75 T | 20 | +18 mm on D |
| NU208 | NU 2 Series — Light | Cylindrical roller | 80 | 18 B | 20 | +18 mm on D |
| NU2208 | NU 22 Series — Wide light | Cylindrical roller | 80 | 23 B | 20 | +18 mm on D |
| 22208 | 222 Series — Wide light | Spherical roller | 80 | 23 B | 20 | +18 mm on D |
| 6308 | 6300 Series — Medium | Deep groove ball | 90 | 23 B | 25 | +28 mm on D |
| 1308 | 1300 Series — Medium | Self-aligning ball | 90 | 23 B | 25 | +28 mm on D |
| 2308 | 2300 Series — Medium, wide | Self-aligning ball | 90 | 33 B | 25 | +28 mm on D |
| 30308 | 30300 Series — Medium | Tapered roller | 90 | 25.25 T | 25 | +28 mm on D |
| NU308 | NU 3 Series — Medium | Cylindrical roller | 90 | 23 B | 25 | +28 mm on D |
| NU2308 | NU 23 Series — Wide medium | Cylindrical roller | 90 | 33 B | 25 | +28 mm on D |
| 21308 | 213 Series — Medium | Spherical roller | 90 | 23 B | 25 | +28 mm on D |
| 22308 | 223 Series — Wide medium | Spherical roller | 90 | 33 B | 25 | +28 mm on D |
| 6408 | 6400 Series — Heavy | Deep groove ball | 110 | 27 B | 35 | +48 mm on D |
24 series across seven 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 / ISO 15 / ISO 1206) — 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.