Chuck,
http://www.roymech.co.uk/Useful_Tables/ISO_Tolerances/ISO_LIMITS.htm has posted links for both hole and shaft size values for each class of fit. If you think of it as being the old ANSI/SAE fit class (Shrink Fit, Press Fit, Transitional Fit, Locational Fit, Sliding Fit, Running Fit, or Clearance Fit) tolerance, it will make a bit more sense. The problem is (as always) that such a tabulated approach is fine for non-interference fits at moderate temperatures, but
not for interference fits at moderate temperatures for non-basic steels or for
any application out of the nominal 20°C ± 20°C range.
If I seem a bit
anal retentive about this, I am. I spent four months in the mid-1970's compiling a proposal for a modification of the ANSI/SAE fit standards as part of an ISO simplification effort. Instead, the committee decided to continue using the data that was compiled for the Spanish-American War and WWI as the basis for the "standard."