[BerntR]

First of all, whip, there are two meanings of CF.

1) A fictitious force that seems to pull the club head away from the golfer in a rotary system of reference.

2) A real force that works from the club back on the golfer, pulling the golfers hands out - and working towards stretching everything between the sweet spot and the swing center.

I don't have the book in front of me, but as far as I can remember, HK's definition a little bit of both. Club head inertia resisting the golfer's effort to keep the club head in orbit. Or something like that. This could be interpreted as a force that works the club head (fictitious) or a force that works the golfer (real)

The mechanism underlying both those forces is club head inertia, as per Newton's 1st law. Any moving or not moving mass will resist any change of speed or direction. The law applies to every molecule in the golf club. That's all the golf club does. It resists any acceleration.

If the club head is rotating towards a closed face already it will continue to rotate at a constant speed. But an external force has to initiate the rotation. The short and long of it is that the golfer has to create the rotation. There is no magic in CF and there is no magic in Newton's laws.

In a swing, with proper power package alignment, the golfer will close the club face by simply continuing the motion through impact. No manipulation. No deliberate club face closing effort. But it doesn't mean that the club closes by itself. It only seems that way.