On Sat, 15 May 2004 20:10:39 GMT, Cicero wrote:

Have you considered a wood auger bit? They come in quite large sizes
but even the large sizes have a small shank (about 9mm).

As the OP wants joined holes I think an auger bit is the only sensible
approach. Any "ordinary" drill is just going to wander into the
adjacent hole very quickly. Even so I doubt an auger bit will keep
true for 1/2 a meter...

As to the initial problem, interesting. I think I'd end up with a
brute force and ignorance approach of some sort, involving lump
hammers and long sharpened bits of steel bar to split and break up the
timber. Rather than trying to drill accurate 18" deep holes...

--
Cheers
Dave. pam is missing e-mail