bit and with a portion of the side wall being removed from the cylindrical body portion of the cutting head all of the embodiments utilize a short coupling mounted directly to the support member extending across the top of the cutting head reinforcement members may be bolted or welded to the sides of the coupling and the support plate as well this embodiment is especially adaptable for use with pressure drilling rigs finally it is contemplated that a number of smaller openings formed by holes slots or slits may be formed in the upper section of the drilling head as an alternate means to provide additional access to the substrate hole and provide drainage for water during the drilling process the method of using the flightless rock auger is as follows the method of removing a plug of hard substrate from a posthole using a flightless rock auger with a drilling rig comprising the steps of a attaching the flightless rock auger to the drive shaft of a power unit of the drilling rig the flightless rock auger comprising a cylindrical hollow cutting head comprising a hollow cylindrical body defining side walls connecting a top end defining an upper peripheral edge and a lower open end defining a lower peripheral cutting edge including a plurality of.