... ,DTH bits,Down the hole bits,DTH hammer,Hammer,Rock drill,overburden bits, Eccentric Reamer ... drilling starts, the reamer swings out and reams the pilot-hole wide enough for the casing tube to slide down behind ... to be left in the drill hole should be sealed at the bottom of the hole by means of cement grout or ... depth in the bedrock using a conventional drillstring . Down the hole bits