The ANSI inch clearance holes in SW are not from ASME B18.2.8.
e.g 1/4 clearance hole:
Close Normal Loose
SW .257 .266 .281
ASME B18 .266 .281 .297
(apologies if my table format is wonky)
Solidworks' clearance holes are one "size" tighter than ASME B18.2.8.
So where do these clearance holes come from? (i've googled for an hour but came up empty) The best I could find is a reference to ISO 286 and 273. Both of those have a statement "Inch dimensions deleted."
BTW. It sure would be nice of these clearance holes had max/min tolerances per ASME B18.2.8.
Jason C. Wells