Boulder splitting question

[Aterra@zzzzzzz]

Hi Jeff,
    A few more thoughts on your boulder splitting question:
    A pneumatic hammer drill can fracture the boulder in directions you may
not want and cause the boulder to be an unstable foundation base.  A core drill
without any hammer action would be the best solution to avoid fracturing in
directions you do not want.  Any time you drill, saw or chisel a stone it
weakens the matrix in the direction of the force.  If you do this right, you weaken
the stone in the direction you want and can get excellent results.
    You can rent a Hilti Core Drill which can be bolted to the stone and or
strapped.  There are two hilti models:  DD160 & DD130.  The 130 is a hand held
option, the 160 is mounted on a track.  You can also get a series of
extensions that you can add as you drill.  I have both these setups and have core
drilled horizontally and vertically up to 36" deep.  The advantage of this method
is the core drill is non pneumatic and does not weaken the stone in unwanted
directions.  You can then have much better success with a series of plug and
feathers.
    Another option is to hire a coring company with drills and saws to
decapitate the rock.  Most core companies have the ring saw Tomas suggested, they
also have Diamond Chain saws which can plunge cut up to 18" deep.  Both these
options would avoid the unwanted fracturing.  I have hired Core companies to cut
openings in 18" thick Stone foundations.  The prices range from $250-1,000
for various size cuts.
    For what it's worth.
Patrick Healy