this is from ebonite's website
Balance holes are non-gripping holes drilled into the ball to adjust the static weights and to create dynamic influence. As mentioned in an earlier tip, the effect of static weights is extremely minimal on the ball's reaction. So the major influence in the effect of a balance hole lies in the effects that it has on the ball's dynamics, those forces affecting the ball when it is in motion.
The location of a balance hole with regard to the distance from the pin is the primary tool for altering the dynamics of the ball's core. From the past tips, we know that the strength of the core is measured by the difference of the RG of the height of the core and the RG of the width of the core. This is called Differential. The greater the difference between the height and the width, the higher the Differential. Higher Differential results in more track flare potential, and will induce the ball to release energy quicker when the ball encounters friction. The breakpoint will be stronger and will increase the hook potential.
On the ball's surface, the distance from the height of the core to the width of the core is 6 3/4 inches. It is within this range that we can alter the flare potential of the ball's core by drilling a balance hole. The height of the core is represented by the pin, or the colored plug on the ball's surface. This is where the core is pressed and suspended in the mold during the pouring of the coverstock. Should we choose to drill a balance hole into the pin, we would be drilling into the tallest part of the core. This would result in a shorter core and lower the flare potential of the ball. While this is not desirable for the vast majority of bowlers, it will be effective if the overall hook of the ball is excessive. Jason Couch won the 1993 Tums Classic with a Crush/R drilled in this manner. Reactive balls first were in their infancy and the lane conditions had not caught up to their power potential, nor Jason's.
If drilling a balance hole into the pin reduces flare potential, we know that drilling a balance hole 6 3/4 inches will increase flare potential. This balance hole will remove mass directly into the side of the core, decreasing the width, and increasing the differential. 6 3/4 inches from the pin will be the maximum strength position for a balance hole, regardless of the pin's position relative to the PAP. Drilling a balance hole halfway between the pin and 6 3/4 (or 3 3/8 inches from the pin) will have little effect on the overall flare potential of the ball. It is located halfway between the height (pin) and the width (6 3/4 inches from the pin) and will remove relative equal amounts of height and width.
With today's higher flare core designs, we must be cognizant of the location of a balance hole with regards to the ball track, especially with a bowler's medium to high rev rate. Balance holes past the PAP, which is where a hole 6 3/4 inches from the pin would be located, will most often fall within an area where the ball track flares into. To ensure that a balance hole location will be flare safe, stack several pieces of tape on top of each other and place them on the location of the intended balance hole. Throw the ball down the lane. If the ball hits the tape pieces and starts to "rumble", you will need to choose another location closer to the PAP. As a rule of thumb, you can assume that 4 1/2 inches or more away from the pin will increase flare potential.
