A drilling device suitable for drilling a pipe under load, comprising a connection part configured to be removably fixed to a tap of a bypass collar, as well as a cutting tool that can be displaced relative to said connection part, configured to pass through said tap to allow drilling the pipe, said drilling device comprising: - a shaft coupled at one of its ends to the cutting tool; the other end of the shaft being intended to be connected to motor means for rotating the cutting tool, - a body rigidly integral to the connection part, - a first part, slidably movable relative to said body along a limited travel, thanks to guide means between said first part and said body, directed in a direction parallel to the shaft, - a second part, rotatably movable relative to said first part thanks to rotational guide means between said second part and said first part, of axis coincident with that of the shaft, said second part comprising a means for removably fixing said shaft, - elastic means configured to constrain said first movable part relative to the body in the drilling direction, - means for loading said elastic means said device being configured so as to allow a drilling during which the drilling force and the forward movement of the cutting tool are provided only by the elastic means, characterised in that the loading means comprise: - a third part, slidably movable relative to the body and relative to the first part, said elastic means being provided to be compressed between a bearing formed on the third part, and a bearing formed on the first part so that said elastic means are configured to be compressed by displacement of the third part relative to the body, while the first part remains fixed relative to said body, - an operating mechanism between the body and the third part configured to ensure the displacement of the third part on the body in the direction of drilling said operating mechanism being configured to assume two positions, including a rest position (Pr) wherein the third part is in a position remote from the connection part, and a working position (Pt) wherein the third part is in a position close to the connection part, said operating mechanism being configured to ensure the compression of the elastic means by switching from the rest position (Pr) to the working position (Pt) when the first part is slidably blocked by said shaft then fixed to the second part, the cutting tool then abutting against the pipe. - a shaft coupled at one of its ends to the cutting tool; the other end of the shaft being intended to be connected to motor means for rotating the cutting tool, - a body rigidly integral to the connection part, - a first part, slidably movable relative to said body along a limited travel, thanks to guide means between said first part and said body, directed in a direction parallel to the shaft, - a second part, rotatably movable relative to said first part thanks to rotational guide means between said second part and said first part, of axis coincident with that of the shaft, said second part comprising a means for removably fixing said shaft, - elastic means configured to constrain said first movable part relative to the body in the drilling direction, - means for loading said elastic means - a third part, slidably movable relative to the body and relative to the first part, said elastic means being provided to be compressed between a bearing formed on the third part, and a bearing formed on the first part so that said elastic means are configured to be compressed by displacement of the third part relative to the body, while the first part remains fixed relative to said body, - an operating mechanism between the body and the third part configured to ensure the displacement of the third part on the body in the direction of drilling said operating mechanism being configured to assume two positions, including a rest position (Pr) wherein the third part is in a position remote from the connection part, and a working position (Pt) wherein the third part is in a position close to the connection part, said operating mechanism being configured to ensure the compression of the elastic means by switching from the rest position (Pr) to the working position (Pt) when the first part is slidably blocked by said shaft then fixed to the second part, the cutting tool then abutting against the pipe.