the invention relates to a drilling tool comprising : two pairs of rotary drums in axial alignment on parallel axes ; motor means for driving rotation of said drums ; support means ; and a support structure on which said drums are mounted to rotate and serving to connect said drums to the support means ; said tool being characterized in that said motor means are mounted inside the drums ; and in that said support structure comprises a plate forming bearings at its bottom ends for said drum ; and a mounting pad for fastening to the support means , the top edge face of the plate connecting said pad to the bearing - forming means .