I've mentioned a few times who I have had drill my balls over the years. A memorable one was when I was in the military stationed in Okinawa. The guy who drilled my ball, a 3-dot Amflite Magic Line, was very precise and I kept that ball for many years - the guy spoke no English but he followed my diagram to a tee. And then there was Jim Lewis, a local PBA member, now retired who drilled all of my stuff during the era of plastic balls. Jim would introduced me to oval holes, greatly increasing my comfort and decreasing my blisters/calluses. He'd take up to an hour shaping those holes by hand. Jim would also take great delight in how close he could come to the static weights I asked for - usually within an 1/8 of an ounce. My current driller, Karl Wolf, a senior PBA member, is alway right on the money - zero tolerance. Before he got involved in the bowling business as an owner and Pro Shop
operator, he was a machinist and it shows. Karl keeps a record of every ball he ever drilled for me on a laptop computer
and his drill press is computerized also. One other thing, Karl has drilled enough balls for me that he knows that my span isn't going to change. Therefore he feels confident enough to mark the hole locations with a mat knife with a razor point so that there is no width of a pencil line error that might occur if a wax pencil were used. That's where the zero tolerance comes in.
I've had a few bad experiences over the years. The worst one was when I got away from the palm lateral pitch in my thumbhole instead of the under the palm pitch I asked for. The guy kept insisting that he drilled it correctly until his son came in and said "Dad, it's the wrong pitch." Then the guy got mad and kicked me out of his Pro Shop