I don't contend to be an expert or engineer on the matter but have balanced a few props and flywheels. In layman's terms...

I have a High Point brand static balancer from B&B but the Dubro balancer is nice too. Windsor prop makes a nice one but it is dedicated to props with a certain hole size. The Top Flite Balancer is fine for small props under 12".

Anyway, as you start balancing a prop by your favorite method of removing material from the heavy blade or painting the light blade, you will eventually find that the prop may balance with one side of the hub down but not with this side up?

As the differential weight between the two blades gets to a value near or below the imbalance of the hub, you will find yourself removing material from the hub instead of the prop blade. Due to not being able to determine the actual vector of the imbalance, you will find yourself chasing the heavy area until the prop or flywheel comes into complete balance? This all tends to just go in one direction unless you over correct.

The Windsor balancer has the arbors fashioned into a clamp. You move these arbors about the prop until you find the balance point. Then you drill a new (larger) hole through the hub using a part of the hub clamping device as your drill guide. This new hole will be at the static balance point of the prop. With this sytem, you are not removing material from a blade or from one side of the hub.

Enjoy,

Jim