Needle roller bearings are separable radial bearings with very low sectional heights that feature high load carrying capability. Needle roller bearings use long, slim rollers, the so -called "bearing needles" as rolling elements. Due to the possibility of mounting inner and outer rings of needle roller bearings separately, mounting becomes much simpler, even under the conditions of mass production. The comparatively thin - walled needle roller bearing rings are usually mounted with tight fits.

In the case of bearing arrangements which work in very limited space, (e.g. gear boxes), needle roller bearings are frequently used without inner rings, designation (RNA). In these cases the bearing needles run directly on the shafts surface. These running surfaces, however, must to be designed to the same quality standard as for bearing rings, (e.g. hardened and ground). Since needle roller bearings allow for length compensation of a certain amount within the bearing, they are optimum as non - locating bearings.

For applications where the non - locating bearings require large axial displacement, and it is not technically or economically feasible to harden and grind the shaft surface, needle roller outer and cage assemblies can be combined with separable wider inner rings.

Needle Roller Bearings are available in several designs including variants without inner rings. The most important design variations are shown on the opposite page.

The bearing outer rings, together with a needle roller set and cage form a unit. To guide the bearing needles, the outer rings have flanges. These are either integrated solid ribs, or in the case of small needle roller bearings, separate pressed in side-plates,(see below b).

To enable simple relubrication, needle roller bearing outer rings are produced with a relubricating groove and lubricating holes in their outer rings as standard features. The exceptions being small needle roller bearings, (see c and e).

Needle roller bearings with machined ringsare usually of single - row design with the exception of bearings of the series NA 69 (see below) or RNA 69 (see f below), respectively, which are produced in double row design (from a specific size onwards).Sealed Needle Roller Bearings

Series NA 48 and NA 49 needle roller bearings are also available in sealed design, either as a single sealed (suffix RS, see below g and h) or double sealed (suffix .2RS, see see below j and k)., respectively.

These bearings are equipped with contacting seals made from wear - resistant synthetic nitrile rubber (NBR) this prevents contamination by foreign particles and impurities.

The seal material is suitable for operating temperatures of -30 deg C up to + 120 deg C.

All information courtesy NKE Bearings Austria www.nke.at