Found this site with some interesting info:
http://www.bowling-info.com/index.php?template=FAQ#AFFECTS%20OF%20SPAN%20AND/OR%20PITCH%20CHANGESDRILLING
AFFECTS OF SPAN AND/OR PITCH CHANGES back to top
All L/R pitches are from a RH point of view when refering to soreness.
When refering to L/R for fingers and thumb it is when looking at the back of the hand.
Thumb Pitches:
+ Reverse = Earlier thumb exit, increased grip pressure may be required, possible soreness to the front or back of the thumb.
+ Forward = Later thumb exit, reduced grip pressure may be required, possible soreness to front or back of the thumb.
+ Left = Reduced axis rotation, possible soreness to right side of the thumb at the tip and left side at the base.
+ Right = More axis rotation, possible soreness to the left side of the thumb at the base and right side at the tip.
Finger Pitches:
+ Reverse = Less lift, earlier finger exit, reduces rotation, possible soreness to the pad side.
+ Forward = More lift, later finger exit, increased rotation, possible soreness to nail side, or broken blood vessels under the nail.
+ Left = Axis tilt enhancer if all pitches are biased left from your normal pitches, possible soreness to right side of finger tip.
+ Right = Possible soreness to left side of finger tip.
Span:
+ Span = More loft, more axis rotation, more reverse required, possible soreness; thumb tip nail side, thumb base away from nail, blood under thumb or finger nails, finger pads.
- Span = Less loft, less axis rotation, more forward may be used, possible soreness; at the crease of first knuckle on fingers away from nail, thumb knuckle nail side, blood under thumb nail (clipping), thumb side away from palm.
SPAN CHECK back to top
With your thumb fully inserted into the ball lay your fingers across the finger holes the midway point between the first and second knuckles should be even with the edge of the hole closest to your thumb.
SARGE EASTER GRIP back to top
Drilling middle finger fingertip while drilling ring finger conventional.
Mostly used by power players to get more consistent release, cut down some revolutions and sideroll
COKE BOTTLE TEST back to top
This test is used as a starting point for finding your ideal Lateral Thumb Pitch. If you do not have a Coke bottle you can also use your no bowling forearm/wrist by placing your hand around the point on your arm to where your thumb almost touches your fingers.
Table:
Index finger = 1/8 lateral away from palm
Between Index and middle = 0
Middle = 1/8 lateral under palm
Between middle and ring = 1/4 lateral under palm
Ring = 3/8 lateral under palm