The Drilling Angle
The Drilling Angle is found by measuring the angle formed by a line from the Pin to the PSA, in asymmetric balls, or a from the Pin through Center of Gravity on symmetric balls and the line created by the Pin to the PAP.
The size of this angle determines how soon the ball starts to transition from skid to hook. This is known as the first transition. In a nutshell, the drilling angle is an indicator of length.
In the guidelines set down by Mr. Pinel, he recommends drilling angles be no less than 10° and no more than 90°. The higher the drilling angle, the more skid you get, the further down lane the ball gets before it starts to hook. The lower the drilling angle, the sooner the ball starts to hook.