Patent ID: 6942046

Claim:
A bore bit comprising: a bottom part having an active bottom face and a top face that is substantially parallel to the active face; a top part having a top face provided with members for fastening to support cables and a bottom face facing the top face of the bottom part; and means for limiting the extent to which the two parts can move apart, while allowing them to move towards each other; said bore bit further comprising: a cylindrical axial bore passing through said two parts; a cylindrical guide penetrating freely in said axial bore; and at least one ramp-forming recess opening out into one of the facing faces and at least one ramp-forming extension projecting from the other of the facing faces to co-operate with said ramp-forming recess in such a manner that movement of the top part towards the bottom part is converted into rotary movement of said top part about the common axis of the axial bore and the cylindrical guide, with the stopping of rotation of the top part imparting rotary movement to the bottom part.