On Fri, 12 Mar 2010 18:41:45 -0800 (PST), Sonny
wrote:

On Mar 12, 4:48?pm, wrote:
On Fri, 12 Mar 2010 07:11:15 -0800 (PST), Sonny
wrote:

A spade bit might have a rough punch-through, so go slow and have
patience at the end point. ?Make sure the bit is sharp. ?I think I
would try welding a spade bit onto a 1/2" pipe and make a separate
chuck insert (fitted/welded onto a 1/2" sleeve, for the pipe) for
fitting into the drill chuck. ?A spade bit is a lot cheaper than an
auger bit for a one-time use (once welded).

If access space, in starting, is limited, also, the 1/2" pipe can be
in successive 24" - 36" sections. ?Any connecting sleeves will pass
through the 1-1/2" holes and the chuck insert fitting can be moved
back, as each successive pipe section is attached. ?Save the set-up
for future use (???, LOL) and use the pipe sections for pipe clamps.

Sonny

?I tried the spade bit first ( on a test piece, out in the open) and
the breakthrough was BRUTAL. The forstner is self guiding and worked a
real treat.

Glad the pipes/extensions worked. That seemed the logical approach.
I didn't think of using a forstner bit and I'll remember the lesson of
that big of spade bit. I've never had to use one that big. And you
still have the pipes for clamps!

Sonny
Thanks Sonny - you were about the only respondent that even
considered my plan might work. Asked the "boss" what the chances were
that I might use the setup again in my lifetime (I'm 58) and he just
laughed.

If I had to pull the bit back out the holes it might have been a
problem, but I was able to reach in the access hole where the
electrical boxes will be mounted, 13 feet in, and release the bit with
an allen key, tie a twine on the end of the extension, and pull it
back out the hole. The twine will pull in the cable on Monday.