Radial internal clearance
SKF super-precision cylindrical roller bearings manufactured to the SP tolerance class are supplied with C1 radial internal clearance (no designation suffix) as standard.
On request, bearings in the N 10 and NN 30 series can also be supplied with a special reduced radial clearance (smaller than C1), when a minimum operating clearance or a preload after mounting is required. For information about clearance values and availability, contact the SKF application engineering service.
Bearings made to the SP tolerance class, particularly those in the NNU 49 series, are also available with a radial internal clearance greater than C1. When ordering, the requisite clearance should be indicated in the designation by the suffix:
- SPC2 for clearance greater than C1
- CN for Normal clearance, greater than SPC2
C3 for clearance greater than Normal
The values for radial internal clearance are listed in table 1. They are in accordance with ISO 5753-1:2009 (except for SPC2) and are valid for new, unmounted bearings under zero measuring load. SPC2 radial clearance values deviate from those standardized for C2. The clearance range is reduced and displaced toward the lower limit.
To achieve the required radial internal clearance, the rings of individual bearings are matched at the factory, marked with the same identification number and usually packaged together in a single box. Be sure to check that the numbers on both rings match prior to mounting. Any mismatch could have a negative impact on the radial internal clearance and the performance characteristics of the final assembly.