From my seat in my home office I could see the missing wiper arm
glaring at me, waiting for me to get the time to pull the dash and
install the $$$ wiper arm shaft assembly to replace the one that I
torqued to death after my cat had done his final pullup on it. So,
being the nice day it was, I came to a stopping place--workwise--about
an hour ago and thought about Frank Condelli's advice to drill and tap
the shaft. The led to me reaching for a big flat file, and that led to
grabbing a centerpunch and hammer just to see what would happen. Off
center. Grabbed the file and flattened the shaft end again in a few
seconds, and this time grabbed a 5X jeweler's loupe and got that punch
right in the center and whacked it. I step drilled up to the size for
a 6MM x 1.0 bolt and quickly tapped it to about 3/4 inch deep.

It worked beautifully. I'm keeping the new assembly in the car just in
case, but if it ever breaks again, at least an easy out will do the
job, and no need to pull the dash. The top of the shaft is 6mm, so
there is no room for error on the centering. Using the jeweler's loup
helped get it perfect. I took a photo for the unbelieving.

Jim