NA4838 Single-row Needle Roller Bearing With Machined Rings
NA4838 is a single-row needle roller bearing with machined rings, extra-light series, with a 190 mm bore, a 210 mm needle complement diameter, a 240 mm outside diameter and a 50 mm width. Those numbers — the bore, needle complement diameter, outside diameter, width and the 1.5 mm minimum chamfer — are ISO 1206 standard values, identical for every manufacturer.
Dimensions
All NA 48 Series designations- Designation
- NA4838
- Type
- Single-row needle roller bearing with machined rings — radial
- Bore code
- 38 — 190 mm
- Bore d
- 190 mm (7.4803 in)
- needle complement diameter Fw
- 210 mm
- outside diameter D
- 240 mm
- width B
- 50 mm — the assembled width
- Chamfer, r s min
- 1.5 mm — minimum, not nominal
- Radial section
- 25 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 190 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 38 gives 190 mm. The four exceptions are 00, 01, 02 and 03 at 10, 12, 15 and 17 mm.
Position in the series9 of 15 in NA 48 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 na48-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 190 mm shaft would take instead
| Designation | Series | Type | D | Overall size (B / T / H) | Section (D − d)/2 | vs NA4838 |
|---|---|---|---|---|---|---|
| NA4838 | Extra-light — this bearing | Needle roller | 240 | 50 B | 25 | — |
| 6038 | 6000 Series — Extra-light | Deep groove ball | 290 | 46 B | 50 | +50 mm on D |
| 6238 | 6200 Series — Light | Deep groove ball | 340 | 55 B | 75 | +100 mm on D |
| 6338 | 6300 Series — Medium | Deep groove ball | 400 | 78 B | 105 | +160 mm on D |
4 series across two 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.