Heres the link to the drill sheet http://stormbowling.com/pdf/drill_specs/key_drilling.pdf
In the drilling instructions it says that the Shift is a "y spinning ball". What exactly does that mean? I have attended a few seminars and recall them saying the the x spinning balls are the most common because it gives the bowler the most predictable and desirable reaction. Also do you know of any other balls that were y spinning? I think the EMB was one.  Thanks

That is/was a good explanation in a nutshell. On "normal" balls/cores, only the X and Y axis matter, they define the RG max/min as well as the differential. If you want, you can describe them as an axis through the pin and an axis in a right angle to this, when you look from the side of a ball at it with the greatest difference (weight distribution will also have effect).
The "additional" Z axis is the 3rd dimension of a core which come into play with strong mass bias cores, the "Preferred Spin Axis" around which the rotating core wants to stabilize, relative to the ball's path.
Without this additional power, it is rather irrelevant (but still there!) and you can find it on any ball when you draw a 6.25" line from the pin through the CG.

If you want, the X/Y/Z stuff is just a different lingo for a core with a strong or significant mass bias influence. Sounds important, but physics work the same on every core.
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Edited on 2/27/2007 9:31 AM