Abstract: The present invention relates to an apparatus in tools for down the hole drilling, which comprises a pilot drilling bit (10), a reamer (8) and a pilot body (1) which is disposed to support the reamer (8) and the pilot drilling bit (10) at the end of a casing tube (2), with the reamer (8) on the one hand in a closed position in which the parts of the tool are concentric with one another and displaceable through the casing tube (2), and on the other hand, an open position in which at least a part of the reamer (8) is located radially outside the casing tube (2), the pilot body (1) being provided with a male portion (7) which extends through the reamer (8) and is in engagement with the pilot drilling bit (10) for transferring rotation and percussion energy to at least the pilot drilling bit (10).