D ee P H o L e DR i LL e R 1 2013 17 Once a 15inch socket is cr eated in the limestone W ayne Findlay switches fr om mud to air to put the QL 120 to work W ith a 15inch concave bit rate of penetration was anywher e fr om 10 to 15 inches per minute in fractur ed limestone below Helper Mike McCaw pr epar es the QL 120 with 15inch bit for hoisting The cr ew will use both the main and auxiliary lines to guide the big hammer into place Then two collars totaling 7000 pounds will stand between the hammer and 6 inch pipe