NA 49 Series Needle Roller Bearings

The needle roller series most designs land on: a NA4900 is 10 mm bore, 14 mm needle complement, 22 mm outside diameter and 13 mm wide, and the series runs to NA4928 at 140 mm bore, 190 mm outside diameter and 50 mm wide. The series number is not decoration and not a diameter series on its own — 49 is the dimension series, width series 4 with diameter series 9, both taken from ISO 15. Diameter series 9 is the same outside-diameter ladder as the 61900 deep groove series, which is why a NA4920 and a 61920 are both 140 mm across; the needle series is the same envelope in a much wider ring. The three bores that break the usual ×5 bore code — 22, 28 and 32 mm — are in this series, written NA49/22, NA49/28 and NA49/32.

Reading the designation. NA4900 is NA, then 4, then 9, then 00. NA is the type — a needle roller bearing with machined rings, complete with its inner ring. The 4 is the width series and the 9 the diameter series, and both are ISO 15's digits rather than this library's: that is why the sentence above can point at a deep groove series and mean it. Diameter series 9 is the ladder the 61900 stands on, so every NA49 diameter is identical to its 61900 counterpart and only the width moves. The bore code is the familiar one — 00, 01, 02 and 03 are 10, 12, 15 and 17 mm, and from 04 upwards it multiplies by five — except for three bores in this series, 22, 28 and 32 mm. Those are not multiples of five, so the two-digit code cannot express them at all and they are written NA49/22, NA49/28 and NA49/32, naming the bore directly.

Fw is the number that makes this type different. Every other type in this sub-library is fixed by three dimensions plus a chamfer. A needle roller bearing is fixed by four, because the needle complement has a diameter of its own: Fw, the inscribed circle the rollers run on, which on a bearing with an inner ring is that ring's raceway. It lies between the bore and the outside diameter, and it is not decoration — the front view above draws it as the circle between d and D and puts the rollers in the band between Fw and D, not between d and D. On a NA4900 that band is 4 mm deep while the whole bearing is 6 mm from bore to outside: two thirds of the radial section belongs to the rollers and the ring behind them, and a third to the inner ring.

What the type buys, and what it costs. Needle rollers are thin cylinders, so a complement packs a long line of contact into a narrow radial band — that is the whole point, and it is why this type exists where a ball bearing of the same outside diameter cannot be fitted. The costs are equally visible in the table. Axially the ring is wide: the same 10 × 22 envelope is 13 mm here against the deep groove 61900's 6. Alignment is the other cost — a needle complement tolerates very little shaft deflection, and the ring offers no self-aligning seat. How much radial load a given bearing carries, and how fast it may turn, are catalogue values for the individual part and not properties the boundary dimension plan fixes, so neither figure appears here.

One chamfer value, and it comes from two other standards. The pages carry a single r s min, which is what ISO 1206 lays out for this type; the numeric limits behind it are ISO 582's, the same chamfer table the other types use. That is why there is one value here rather than the per-ring pair a cylindrical roller bearing would need — the boundary dimension plan for a needle roller bearing states one minimum for the corner, so one column covers it.

Why no clearance table is printed on these pages. ISO 5753-1 gives needle roller bearings a radial clearance table of their own, and these bores fall inside it — so unlike the tapered and thrust types, the figure exists. What stops it appearing here is the reproductions: the catalogue versions consulted disagree in every clearance group, so none can be confirmed as the standard's own and this library does not publish a figure it cannot attribute. The ISO 5753-1 page sets out both readings side by side.

What is not in this series. Dimension series 59 and 69 are needle roller series too and their designations exist, but they are not tabulated here yet. RNA types — the same bearing without its inner ring, running directly on a hardened shaft — are a separate family and are not collected. Drawn cup needle roller bearings belong to ISO 3245, not ISO 1206, and are not here either. Each of these is a deliberate boundary rather than an omission, and the roadmap below records them.

Every designation in the table below links to its own page with the ISO 1206 boundary dimensions, the bore-code arithmetic, the needle complement diameter and the same-bore comparison against every other series and type.

This series runs from a 10 mm to a 140 mm bore. The sub-library as a whole reaches 300 mm, and the widest single bearing in it is a 6360, 620 mm across, in the 6300 series. This one stops short of it.

d = bore diameter, Fw = needle complement diameter, D = outside diameter, B = width. All of them are ISO 1206 standard values and are the same for every manufacturer. r s min is the minimum single chamfer dimension the plan gives; its matching maximum is in ISO 582, which is why the column says “min” and not an equality. The last column is derived: radial section = (D − d) / 2, the wall thickness you are working with when you size the housing. No load rating and no limiting speed appears here — see the bearings index for why.

Outside diameter × overall size in millimetres, for the 5 smallest bores in this database. The full charts, one per type, are on the bearings index. Reading a row is what a machine designer does when the shaft is already fixed: the bore does not change, the housing bore does. Across the type boundary the last number changes meaning — it is a width above and a height below — so compare within a type, then decide whether the job wants a ball bearing, a tapered roller or a thrust bearing at all.