I guess I'll wade in here with my $.02 on how I make the tool.

-- I drilled a 11/32 hole, 2" deep, into the end of a 12" piece of 3/4"
round mild steel rod.
-- 3/4" from the end of the rod I drilled and tapped a 1/4" set screw hole
after having ground a 'flat' at that location.
-- I tapered the end of the steel rod to remove excess metal and to give it
a sharper profile.
-- I intend to add a length (2'?) of 3/4" galvanized pipe to complete the
handle. I'm having a bit of trouble finding a 'new' piece of pipe that will
fit properly as most of the walls seem to be thinner these days and, as a
result, the hole is more than 3/4". Guess I'll visit the junk yard

I found that the corners of the 1/4" HSS bits had to be eased slightly so
that they would fit into the 11/32" hole.

I've taken the larger HSS bits and ground 1 1/2" of one end of each to a
diameter that would fit into the drilled rod. This took a bit of time with
my 6" grinder but the fit is good.

Thanks for the idea Darrell.