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.