Abstract: A cutting tool for a pneumatic hammer operative at the bottom of a hole comprising a head for supporting cutting bits and a tail of reduced diameter extending from the head and provided with grooves forming alternating asymmetrical teeth engageable in symmetrical grooves provided in the interior of the front cylinder of the hammer. Each tooth of the cutting tool has a working flank in contact with the hammer during drilling which is of greater height than the other flank of the tooth so that each asymmetrical tooth can define in the symmetrical groove of the hammer an escape channel for compressed air from the hammer.

Abstract: In apparatus for drilling a hole in the ground comprising tubing for shoring up the walls of the drilled hole and a drilling member comprising a pneumatic percussion hammer having an eccentric cutting edge, the drilling member extending in the tubing and having a working position in which the cutting edge extends below the lower end of the tubing and a removal position in which the cutting edge is within the tubing, the extension tube for supplying gas to the hammer is connected to the hammer by a helicoidal telescopic connection which is rotatable through 180.degree.