A clamping device for releasably holding a tool holder shank formed with an engagement bore in a rear end, comprising: a housing having a forwardly facing surface and a mounting bore intersecting the forwardly facing surface and extending rearward therefrom for receiving the tool holder shank; a drawbar being mounted reciprocally movable inside the housing and which in a forward end is provided with engagement means which is adapted to go into engagement with an engagement formation inside the engagement bore of the tool holder shank, the drawbar being in a rear portion formed with a drawbar aperture extending through the drawbar in a transverse direction in relation to a longitudinal axis of the same; and a cam shaft extending through the drawbar aperture and comprising a cam formation, wherein the cam shaft is rotatably journalled in the housing and adapted to impart an axial displacement to the drawbar in relation to the housing by means of the cam formation when rotating the cam shaft, characterized in that the cam shaft comprises two identical cam formations, which are spaced apart by a recess, and which each comprises a first cam surface operable to urge the drawbar rearward to a locked position, in which it firmly locks the tool holder shank to the clamping device, and a second cam surface operable to positively displace the drawbar forward to an unlocked position in which the tool holder shank is releasable from the clamping device, and that the drawbar on the inside of the aperture is formed with a ridge on each side of the aperture in a direction in parallel to a longitudinal axis of the drawbar which each fits in the recess of the cam shaft when rotating the same. a housing having a forwardly facing surface and a mounting bore intersecting the forwardly facing surface and extending rearward therefrom for receiving the tool holder shank; a drawbar being mounted reciprocally movable inside the housing and which in a forward end is provided with engagement means which is adapted to go into engagement with an engagement formation inside the engagement bore of the tool holder shank, the drawbar being in a rear portion formed with a drawbar aperture extending through the drawbar in a transverse direction in relation to a longitudinal axis of the same; and a cam shaft extending through the drawbar aperture and comprising a cam formation, wherein the cam shaft is rotatably journalled in the housing and adapted to impart an axial displacement to the drawbar in relation to the housing by means of the cam formation when rotating the cam shaft, characterized in that the cam shaft comprises two identical cam formations, which are spaced apart by a recess, and which each comprises a first cam surface operable to urge the drawbar rearward to a locked position, in which it firmly locks the tool holder shank to the clamping device, and a second cam surface operable to positively displace the drawbar forward to an unlocked position in which the tool holder shank is releasable from the clamping device, and that the drawbar on the inside of the aperture is formed with a ridge on each side of the aperture in a direction in parallel to a longitudinal axis of the drawbar which each fits in the recess of the cam shaft when rotating the same.