I found this article abut CLT by Chip Aki, from 2006.
Question: I wanted to post a summary of how Center Line Transposition seems to be defined by those using it. I never really determined if the definition found in practice is what was initially intended, a narrow use of a broader term, or something which evolved into something else. In my understanding, what is below is common to a PBA.com thread, an IBPSIA forum thread, and the BTM thread. If you find any of this in error, please let me know, so that I can edit this post.
Summary:
1) CLT is a fitting technique or method. Not a type of grip per se.
2) Placement of the drilled gripping hole centers is performed from the standard T-line. Only finger pitches, finger insert orientation, or finger oval orientation (no inserts) are referenced from another line (a transposed center line)
3) The transposed center line is just a line that intersects the standard center line at the midpoint of the finger bridge, the angle of which is determined by having the bowler insert the thumb into the thumb hole of either a well fitting ball, or the ball being fitted if thumb already drilled, and relaxing the fingers across the location of the finger holes. A marker is then used to draw a line between the ring and middle fingers which represents the direction of more natural placement of the fingers. This is the transposed centerline.
4) If the ball is being fitted from an existing well fitting ball, the fingers would be drilled applying the same finger pitch specs as in the pattern ball, but now applied about the transposed center line, which is effectively a pitch modification. The magnitude of the pitch change is related to how much angle there is between the transposed CL and the standard CL and also the magnatude of the initial pitches. The grip inserts or any ovaling of the finger holes would also be oriented to the transposed center line.
http://www.neon-auto-lights.com/temp/CLTdrillinginstructions.pdf5) If a well fitting ball is not being used to perform the CLT method, then the Pro Shop Technician, would select the appropriate pitches based upon careful inspection of how the bowlers hand lies across the ball and any other attributes such crooked fingers or inflexible finger joints.
6) Once the ball is drilled using the CLT method, the pitches can be measured referencing the standard centerline and documented and repeated in the future w/o CLT. The angle between the transposed CL and the standard CL would still be needed to set the grip inserts or oval the finger holes.
7) Most bowlers reported an increase in comfort and more contact between the hand and the ball.
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Duke Harding"My choices early in life were either to be a piano player in a whore house or a politician. And to tell the truth, there's hardly any difference." -- Harry Truman
I've learned...That one should keep his words both soft and tender, because tomorrow he may have to eat them.
