Let's start with some basics. The most important part of a bowling ball is surface. Regardless of how a ball is drilled, the surface has more determination on reaction than anything. For example take a pearl ball and drill it to the max and throw it on a lot of oil. More than likely this ball will go straight. Take a sanded solid ball drilled semi strong and this ball will hook circles around the pearl. The point is to be sure you have the proper surface on the ball for the shot you are trying to play. Here is some basic drilling information. These drillings are for two piece symmetrical balls only. Asymmetrical balls such as the Omegas, Offset Hammers, and Timberwolf all have their own drillings to follow.

This drilling is for crankers or bowlers that have slower speed that still turn the ball a little. In this drilling you place the pin under the bowlers middle finger which will put it about 5-6 inches away from the axis point. This drilling creates great length and a big backend. The reason this is called a potential energy drilling is that you have to hit the ball to get the energy out of the ball. By placing the pin so far away from the axis point it creates alot of potential energy. If you throw the ball straight and use this drilling the ball will more than likely go straight. This drilling is excellent for inside lines. The center of gravity can be moved around to tweak the ball for the desired reaction. The center of gravity closer to the pin will create a later roll, whereas the center of gravity further away from the pin will creat a slightly earlier roll.