Tony, I use the exact same triple-beam scale in the school shop, weight-matching rods, pistons, etc., prior to spin-balancing smallblock Chevy crankshafts. We match them to +/- 1/10 gram. Since a dollar bill weighs almost exactly a gram, that's pretty close! I've also got an old 2-pan beam-balance scale my father used to use on flathead Furd parts back in the late 40's, and it still works. I just have to find the lightest part with that one, and use it as a reference while I match the other pieces to it.
BTW, some of the race wrist pins I use come with instructions NOT to try to balance by machining the pin ends. If the pin is running against a lock ring in the piston boss, machining the hardened end surface away might result in premature wear. Be careful!
Jerry
