The invention relates to a wrench for use with drilling apparatus and which serves for loosening adjacent drill bit segments of a drill bit during drilling of extended holes into the ground and where this involves the insertion of, or the removal of, extension segments from the drill bit. The wrench includes a pair of carrier members whereby it is supported on the support structure of a drilling apparatus, as well as a pair of gripping members, displaceably supported between the carrier members and between which a drill bit segment can be gripped, and piston/cylinder mechanisms whereby the carrier members, and hence the wrench, can be displaced between an inoperative stowed configuration and an operative configuration and whereby the gripping members can be displaced for gripping a drill bit segment and for loosening the segment with respect to an adjacent segment.