To achieve the required radial internal clearance, the rings of individual N 10 and NN 30 series bearings are matched at the factory, marked with the same identification number and packaged together in a single box. Always check that the numbers on both rings of these bearings match prior to mounting. Any mismatch could have a negative impact on the radial internal clearance and the performance characteristics of the final assembly. The rings of NNU 49 series bearings, however, are not marked with an identification number and can be exchanged with rings in the same clearance class.
When mounting super-precision cylindrical roller bearings with a tapered bore, the radial internal clearance or preload must be adjusted accurately. This is done by driving the inner ring up on its tapered shaft seat (fig.1). The resulting expansion of the inner ring determines the internal clearance or preload in the mounted bearing. For proper mounting, the inside or outside envelope diameter of the roller set must be accurately measured. SKF internal clearance gauges in the GB 30 and GB 10 (fig.2) or GB 49 (fig.3) series enable simple and accurate measurements. For additional information about internal clearance gauges, refer to Gauges.
Mounting a cylindrical roller bearing in the NN 30 K series using a GB 30 series gauge is described in the following. The same procedure can be applied when mounting cylindrical roller bearings in the N 10 K series using either a GB 10 or GB 30 series gauge. A similar procedure can be applied when mounting cylindrical roller bearings in the NNU 49 K series using a GB 49 series gauge.
When mounting without the assistance of an internal clearance gauge, be sure that the accuracy of the readings is sufficient for the application requirements.