Have a B&D DR402 Hammerdrill (reversible). Needs keyless chuck. I
think the point I need made clear for me is this: The screw is
Reverse thread (LH thread), right? And you remove it with whatever
tools fits the head (flathead, phillips, etc), right? And THEN you do
the 1/4"-3/8" Allen wrench trick with the hammer counterclockwise
because there is a second set of threads involved here, right? Those
of the chuck itself. Chuck screws on shaft normally then screw/bolt
goes in reverse thread.

Didi i get that right? Never had it spelled out explicitly.

Kevin