Overview: Heavy-duty needle roller bearings consist of a machined and ground channel-shaped outer ring with a complement of needle rollers, and a cage. The high-strength cage retains and guides the rollers. An opti on al lubrication groove and hole in the outer ring facilitates re-lubricati on. These bearings can be used with or without a machined and ground inner ring, depending on the suitability of the shaft as a raceway surface.
® Sizes: 5 mm 一335 mm (0.1969 in. - 13.1890 in.) bore.
Markets: Gear pumps, sheaves, automotive transmissions and two-cycle engines.
Features: Thick outer ring provides maximum load capacity and shock resistance
with a relatively small radial cross section.
Benefits: Optimum speed and lubrication-retention capability.
When it is impractical to finish the shaft to meet the desired raceway design requirements, an inner ring may be used. Standard needle roller bearings are available with inner rings (such as the NA Series) forming complete bearings. Bearings furnished with inner rings meet the quality requirements in accordance with ISO standards.
Whenever the shaft can be used as the inner raceway, needle roller bearings without inner rings provide advantages of economy and close control of radial internal clearance in operation. Tolerance class F6 is the normal specification for the metric series needle roller complement bore diameter of an unmounted bearing as shown in Table 1. In the case of needle roller bearings of series RNAO, without flanges and without inner rings, the outer rings and needle roller and cage assemblies are not interchangeable.
These seals limit the bearing operating temperature between -30° C and 110° C. If the operating temperature must be outside the above range or if the seals are exposed to unusual fluids, external seals using suitable seal materials or other solutions should be investigated. Sealed bearings are normally packed with a high quality lithium soap base grease suitable up to 120° C for short periods of operation. The limiting speeds specified for sealed bearings listed in the bearing tables are based on operating conditions determined by testing. Optimum performance may be expected providing the bearing is properly installed, with appropriate internal clearances, and be subjected to a load of low magnitude. Care should be taken that overheating will not occur, thus preventing breakdown of the grease and eventual bearing failure.