There is a new balancing device that has you shift the center of the hole in the prop to correct for imbalance. Its an interesting concept.

The idea behind this method of balancing is that many wood props have the holes drilled off center a bit, and that is the reason for the prop not balancing. Unfortunately.. the premise does not hold true for the composite propellers.

The way I ream out props is I have a step-tap "screwdriver" made by Klein tools. (carried in the electrical section at most Home Depot stores.) This tool is extremely accurate about keeping the hole centered. When I have tapped out to the same thread as the prop shaft (if its an SAE thread...) then I follow with a reamer to take out the threads. The step-tap cuts better than most prop reamers because it is made to cut metal... most prop reamers are made to cut wood. (and have a hard time with composite props) The prop reamers tend to get dull quickly cutting the Master Airscrew black props and the APC grey props.