the rear end of the body 1 because the guiding element 3 is hence not made to feed for example pressurized medium it can be closed at its end as shown in the drawing because it is now to be used only for the point of attachment of the centering element 6 the guiding element 3 is capable of moving axially with respect to the percussive drill bit assembly 2 which also in this embodiment comprises of a ring bit 7a or 7b and the inner bit 7c also in this construction there is the possibility to supply one or several forces required by the operation of the apparatus through the guiding element 3 such as the advancing movement traction in the guiding element 3 which is supported by the body 1 of the drilling apparatus there is in radial direction i e in a direction perpendicular to the longitudinal direction of the pipe to be drilled a wider centering element 6 which as mentioned hereinabove can be freely rotating with respect to the element 3 or provided for rotation together therewith the centering element 6 can be dimensioned according to the inner diameter of the pipe to be drilled away and it can also be arranged to be releasable from the guiding element 3 and replaceable with a new.