The surface roughness of the shaft and the housing is only used for the calculation of the interference fit. The effective interference of the parts is reduced by 0.4⋅Rz according (DIN 7190-1, 2017). In previous versions, a reduction of 0.8⋅Rz was used as in the previous version of the standard.
More precisely for the surface roughness of the shaft, the sum of roughness of shaft and inner ring should be entered. Similar for the outer ring. As the roughness of the bearing is usually smaller that of shaft and housing, this might be ignored in most cases.
