[Weightshift]

..but when in the downswing does this karate chop occur?

My question has been answered in another thread:
http://www.lynnblakegolf.com/forum/s...ead.php?t=3064
#2 Drilling the Correct Downstroke Motion

"The cure is to learn a proper Downstroke. First, make sure your Start Down is On Plane. Do many Start Down Waggles to assure that you are pulling the butt-end of the Club directly toward the Plane Line. Then, take this motion into the Release area, making sure you Uncock and Roll while still driving toward -- not down -- the Plane Line. Finally, complete your Total Motion by Swiveling out of the Follow-Through (Both Arms Straight position) and into the Finish. Make sure the butt-end of the Club points toward the Plane Line as you Finish Swivel."

Thanks