The boundary dimensions of NSK bearings show in fig as below.
NSK bearing dimensions are the dimensions that define their external geometry. They include bore diameter d, outside diameter D, width B, bearing width(or height) T, chamfer dimension r, etc. It is necessary to know all of these dimensions when mounting a bearing on a shaft and in a housing. These boundary dimensions have been internationally standardized (ISO15) and adopted by JIS B 1512 (Boundary Dimensions of Rolling Bearings).
The boundary dimensions and dimension series of NSK radial bearings, tapered roller bearings, and thrust bearings are listed in Table NSK bearing size chart.
In these boundary dimension tables, for each bore number, which prescribes the bore diameter, other boundary dimensions are listed for each diameter series and dimension series. A very large number of series are possible; however, not all of them are commercially available so more can be added in the future. Across the top of each bearing table, representative bearing types and series symbols are shown (refer to NSK bearing nomenclature).
The relative cross-sectional dimensions of radial bearings (except tapered roller bearings) and thrust bearings for the various series classifications are shown in figs as below.
Comparison of cross sections of NSK radial bearings for various dimensional series
Comparison of cross sections of NSK thrust bearings for various dimensional series
The dimensions of NSK bearings of snap ring grooves in the outer surfaces of bearings are specified by ISO 464. Also, the dimensions and accuracy of the locating snap rings themselves are specified by ISO 464