A cutting tool assembly, preferably a rotating cutting tool assembly, comprising a first tool part having at least one cutting edge, and a second tool part for releasably holding of the first tool part, the first tool part extending along a longitudinal axis (x), wherein the first tool part comprises a forward end portion comprising the at least one cutting edge and a rearward end portion comprising a conical section, tapering away from the forward end portion, and an engagement section located rearwards the conical section, the second tool part comprising a conical recess for receiving of the conical section of the first tool part, and a clamping device located rearwards the conical recess, wherein the clamping device is provided in a transversal cavity of the second tool part and comprises a first clamp block, a second clamp block and a differential screw extending along a transversal axis (y) and engaging the first and second clamp blocks (21, 22), wherein the differential screw is configured to move the first and second clamp blocks (21, 22) in parallel with the transversal axis (y) away from and towards each other, the first and second clamp blocks (21, 22) comprise a respective engagement surface (21b, 22b) arranged to engage the engagement section of the first tool part, when the conical section is placed in the conical recess, in order to pull the first tool part into a holding position in the conical recess when the first and second clamp blocks (21, 22) are moved towards each other, and each of the first and second clamp blocks (21, 22) comprises a respective threaded channel (21a, 22a) extending in parallel with the transversal axis (y) and receiving the differential screw, characterised in that the differential screw is protruding rearwards from the first and second clamp blocks (21, 22) beyond the threaded channels (21a, 22a). the first tool part extending along a longitudinal axis (x), wherein the first tool part comprises a forward end portion comprising the at least one cutting edge and a rearward end portion comprising a conical section, tapering away from the forward end portion, and an engagement section located rearwards the conical section, the second tool part comprising a conical recess for receiving of the conical section of the first tool part, and a clamping device located rearwards the conical recess, wherein the clamping device is provided in a transversal cavity of the second tool part and comprises a first clamp block, a second clamp block and a differential screw extending along a transversal axis (y) and engaging the first and second clamp blocks (21, 22), wherein the differential screw is configured to move the first and second clamp blocks (21, 22) in parallel with the transversal axis (y) away from and towards each other, the first and second clamp blocks (21, 22) comprise a respective engagement surface (21b, 22b) arranged to engage the engagement section of the first tool part, when the conical section is placed in the conical recess, in order to pull the first tool part into a holding position in the conical recess when the first and second clamp blocks (21, 22) are moved towards each other, and each of the first and second clamp blocks (21, 22) comprises a respective threaded channel (21a, 22a) extending in parallel with the transversal axis (y) and receiving the differential screw, wherein the clamping device is provided in a transversal cavity of the second tool part and comprises a first clamp block, a second clamp block and a differential screw extending along a transversal axis (y) and engaging the first and second clamp blocks (21, 22), wherein the differential screw is configured to move the first and second clamp blocks (21, 22) in parallel with the transversal axis (y) away from and towards each other, the first and second clamp blocks (21, 22) comprise a respective engagement surface (21b, 22b) arranged to engage the engagement section of the first tool part, when the conical section is placed in the conical recess, in order to pull the first tool part into a holding position in the conical recess when the first and second clamp blocks (21, 22) are moved towards each other, and each of the first and second clamp blocks (21, 22) comprises a respective threaded channel (21a, 22a) extending in parallel with the transversal axis (y) and receiving the differential screw, characterised in that the differential screw is protruding rearwards from the first and second clamp blocks (21, 22) beyond the threaded channels (21a, 22a).