ISO 1206 — Needle roller boundary dimensions
The boundary table behind the needle roller pages here, and the one column in it no other bearing type has: Fw, the diameter of the needle complement.
What it fixes
ISO 1206 does for a needle roller bearing what ISO 15 does for a deep groove ball bearing: it fixes the mounting envelope, so that a complete bearing from one maker fits a shaft and a housing bored for another. The scope is stated once and it settles who the numbers are for — the standard's specifications apply to complete needle roller bearings and to bearings without an inner ring alike, so one table serves both. What the standard tabulates is the nominal boundary dimensions in the four dimension series below, plus the tolerance values for the normal class and the GPS specifications that go with them; this library prints the first and not the second.
The columns of a needle roller tableas the standard names them in its own Table 1
- d
- Nominal bore diameter. On a complete bearing this is the bore of the inner ring, and it is the same bore the deep groove plan would give that shaft.
- Fw
- Nominal bore diameter of needle roller complement — the standard's own wording, and the one column no other plan in this library carries. It is a property of the needle complement rather than of a ring, which is why it is defined whether or not the bearing has an inner ring. On a complete bearing it is the raceway the needles run on; on a bearing without an inner ring it is the bore, and it is the dimension the shaft has to provide.
- D
- Nominal outside diameter — the same outside diameter the deep groove series carries for the same dimension series.
- B and C
- The table header prints these two together and gives one figure, so they have to be told apart from the symbol list: B is the nominal inner ring width and C the nominal outer ring width. A bearing without an inner ring has no B, which is the reason both letters appear in the heading of a table that describes both.
- r s min
- The minimum single chamfer dimension at the ring corner, and only a minimum. ISO 1206 fixes it row by row and then hands the matching ceiling to another standard: its section on nominal boundary and chamfer dimensions says in as many words that maximum chamfer dimensions are in accordance with ISO 582.
The four dimension series the boundary tables defineand which of them this library takes
| Dimension series | Table | In this library | Bore range here |
|---|---|---|---|
| 48 | Table 2 | NA48 — 15 designations | 110–300 mm bore |
| 49 | Table 3 | NA49 — 28 designations | 10–140 mm bore |
| 59 | Table 4 | — | Not tabulated here. |
| 69 | Table 5 | — | Not tabulated here. |
The series themselves come from ISO 15, and the numbers say why: 49 is width series 4 on diameter series 9, and 48 is width series 4 on diameter series 8. The last two columns are read from this library's own bearing data and not from the standard, so they move when the data moves — a series added here changes its own row, and no row can claim a series is absent while a link to it sits on the same page.
The outside diameters are the 61800 and 61900 ladders
A dimension series that shares its diameter series shares its outside diameters, and both series here share theirs with a deep groove family. Diameter series 9 is the 61900 ladder, so a NA4900 is 10 × 14 × 22 × 13 mm while a 61900 is 10 × 22 × 6 mm on the same bore: identical across, in a ring wide enough to hold a full complement of needles instead of a ball raceway. Diameter series 8 is the 61800 ladder the same way. This library does not leave that to the reader — every bore the 49 series and the 619 series have in common is compared cell by cell at build time, and a single disagreement stops the build rather than publishing two pages that contradict each other.
A bearing without an inner ring is the same row
The standard heads its boundary tables with complete bearings and bearings without an inner ring, and that heading is the whole point of printing Fw beside d. Read the row as the no-inner-ring form and Fw becomes its bore while the outside diameter, the width and the chamfer do not change: the designation loses its inner ring and gains an R, so NA4905 and RNA4905 describe one envelope, not two. This library tabulates the complete bearings, and the numbers on its 49 and 48 series pages are that same row.
Why no clearance table is on this page
Clearance is not this standard's subject — it fixes boundary dimensions and tolerance values, and radial internal clearance belongs to ISO 5753-1. That standard does carry a table for needle roller bearings, and this library does not reproduce it, for a reason worth stating in full: the authorities disagree. For a bore of 18 to 24 mm NTN publishes C2 0–30 µm, Normal 10–40 µm, C3 25–55 µm and C4 35–65 µm for interchangeable bearings, and a second, more tightly controlled table for bearings whose rings must not be intermixed. Schaeffler publishes C2 0–25 µm, CN 20–45 µm, C3 35–60 µm and C4 50–75 µm for the same bore band, and cites DIN 620-4:2004, which is ISO 5753-1:2009. Both are named sources quoting the same standard, and they do not agree in any group. A table printed here would be right for one of them and wrong for the other, so the page records the contradiction instead of picking a side; the ISO 5753-1 page states which of its tables do have a page here.