My technique is fairly similar, with as far as I can tell one variation at the end.

I got my basic technique from a Battlin' Blades column, which used to be written by Bill Bagwell and published in Soldier of Fortune, back in the day. The article was probably published in the late 80s.


Any way in this technique like yours you don't really grip the knife hard to start with, you hold it loosely between your thumb and your first finger and it pivots between those digits.
However you do grip the knife far up the handle enough so that if you did close your hand your pinky would be on the handle of the knife.
I.e. you choke back if there is enough handle, but not all the way.
You need to be able to end up with a full grip (thumb and 4 fingers) on the handle.
Like your starting position the pinky is relaxed, but either just sitting loosely on the rear of the handle, or maybe slightly raised, but in a position where it can (and will) end up on the rear of the grip.
The start position is with the arm raised so that the upper arm(elbow to shoulder)/elbow is at least parallel to the ground, but maybe depending on your anatomy pointing up.
The lower arm (elbow to wrist) is pointing back, with the wrist cocked back.
In this position the knife is probably over your shoulder pointing at the ground behind you.
You start your swing by bringing your upper arm down, at the shoulder.
Then as your arm comes down your elbow will start to straighten, but you don't actually consciously straighten your elbow until your upper arm is maybe down say around 45 degrees.
You straighten your elbow until your arm is straight.
At or maybe just before this point your wrist will start straightening.
As your wrist straightens that relaxed pinky is used to sort of flick the rear of the grip up, pushing the tip if the blade down.
This pinky flick starts before the knife is fully straight but after the wrist has started straightening.
This last little flick with the pinky imparts a further explosive acceleration to the arc described by the point of the blade.
The effect is that the pinky, and probably middle and ring fingers do end up gripping the handle, but not until the very end of the stroke.
If you do this through air instead of into a target, you'll end up with your wrist actually pointing down a little.
Over all you start of with a curve of your arm, elbow, wrise and knife and end up with a near stright line, except perhaps that the wrist and knife might be pointing down.
The knife is accelerating the whole way thought and gets its final burst of acceleration with that pinky flick/tightening.
Or course your swing changes if you are chopping sideways, e.g. standing wood, but the idea of the pivot between fore finger and thumb, the last almost explosive flick of power delivered with the closing flick of he pinky and the idea of an ever accelerating, ever straightening arc remain.
I believe that last flick with he closing pinky adds quite a bit of power to the stroke.

The last thing is that I try to chop as far forward on the blade as possible, so I'll be trying to strike the target, just to the rear of the belly of the blade, in order to increase leverage as much as possible.