Originally Posted by Mordan
He means using the tool. If you are holding the club at address, the tool basically allows you to rotate the face horizontally. If you turn the club in your hands you're rotating the face on a diagonal plane because the shaft is on an angle.
Take it to the extreme, you're at address and someone comes along and opens the clubface 10 degrees (without you moving your hands or twisting the shaft). The loft on the face is still the same 10 degrees it was before the adjustment, just the face is now open. So if you now twist the club in your hands to square up the face again, you're going to be reducing the loft as you do it. Hence why for people who square up the face using their hands after making an adjustment, opening the clubface will cause them to reduce loft and closing the clubface will cause them to add loft.
Not sure about Deron, but that doesn't help me. The butt end of the shaft is on the same plane as the rest of it, so tool or not, how are you rotating it any direction other than on said diagonal plane of the shaft?
It can only be something to do with assymetry of the shaft tip, right? Because otherwise, that head is spinning on the same angle if you rotate it around the end of the shaft or if you rotate it and the shaft in my hand. It wouldn't make a difference.
I guess the part that is hard for me (us?) to understand is how the tiny variations in that shaft tip can actually allow the horizontal movement. (Which is why I am a civil engineer, not a mechanical engineer ... I don't like it when stuff moves!)