A drill bit having a central shank having an "S" shaped cutter integrally formed on or detachably secured to the shank. A collar is detachably secured to the shank above the cutter and is keyed to the cutter to prevent rotation of the collar. A generally flat secondary cutter is secured to the collar and has a plurality of depending cutter elements on the peripheral edge thereof as well as a plurality of radially extending chisel cutters depending therefrom.
