.002 is a good FINAL clearance after honing for most piston fits, but requires break-in. Racing types will need to go .003 to .004 for instant RPM's. You have to allow for proper honing and utilize the new piston for your measurement, not a used one.
I usually hone the last thousand or two till I get the proper fit. When fitted properly, a dry piston slipped in a dry cylinder on a nice, flat bench will WHOOSH as it glides through when released. I call this the PUSSY fit!
Sorry for offending anybody that may bat for the other team...I won't go there for them.
Seasoned Motor Builder's Trick for free!!
Micrormeters (inside & outside) are the tool of choice for acquiring this sensitive of a fit. But after doing hundreds, I've come to be able to "feel" it by slipping a long .0015 or .002 feeler gauge in with the piston along the center of a skirt. (Note: don't force it or you're too tight) You should be able to draw the feeler gauge out with the slightest bit of resistance w/o carrying the piston with it.