Dan Belcher,
When you drill a pin out of a ball that has a considerable piece of the core like a flip block on top, or a higher density cap, you can drill some of the diff. out of the ball by drilling through this with a deep hole. It is like using a balance hole, with out the fourth hole. Because you are drilling density out of the ball at that spot, you can alter the amount of flair produced. It isn't that you are drilling the "pin", it is what you are doing to the shape of the core that the pin is holding in place.
When you drill a balance hole anywhere else on the ball, if deep enough, you are altering the shape of the core, basically making it asymmetrical. When drilling through the pin, you are drilling the top of the core, still leaving the outside symmetrical shape intake, but now altering the dynamics of the weight distribution of the core.
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Tommy Gollick
Storm Regional/Pro Shop staff
Red Crown Pro Shop Harrisburg, PA
stormbowling.com