btw, the water jets we used at UMR (University of Missouri-Rolla) were capable of cutting 18 inches into granite. there's a balance between the material used in the water (steel shot, silica, etc.), nozzle size and water pressure that must be adjusted rather precisely for various materials. i think they've got it down to a science now, however.

i particularly worked underneath the st. louis arch cutting out the rock (dolomite) to make way for the IMAX theater. of course, in the end, we had a caterpillar lowered into the hole with a pneumatic jack hammer on the end breaking the rock up for us to haul out in a nifty hopper apparatus my buddy and i designed. yeah. we dug dirt.

the school also used the water jets to cut a mini-stonehenge, which is where dr. summers (the water jet researcher) earned his "fame".

taks