Tony,
When doing final balancing of rods, pistons, wrist pin assys . . . the machine shop that I worked with took an end-mill that was just slightly larger than the wrist pin bore and went in on the ends of the pins to get the weights all within .1 grams for the assembled components.
The pistons were already within .1 grams of each other, but the rods varied a little (+/-0.5 grams) and there were no good places to machine that much material off -
