Interesting.  After reading Glen's post, I went back and took a closer look
(with a set of magnifying lenses) at the drill.  The spindle on mine has no
slots in it.  It is threaded to the end.  There does not appear to be
anything within the spindle that might hold a shaped bit to keep it from
spinning if it were simply inserted into the spindle.  The threaded nut
screws all the way down onto the spindle.  I have not measured the inside
diameter of either the spindle or the nut, but will to compare.

Thanks to all  for the information.

Regards,

Dwight