A clamping device for releasably holding a tool holder shank formed with a bore comprising: a housing having a forwardly facing surface and a bore intersecting the forwardly facing surface and extending rearwardly therefrom for receiving the tool holder shank; a drawbar being mounted reciprocally movable inside the bore and which in a forward end comprises engagement means which is adapted to go into engagement with an engagement formation inside the 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 first and second spaced apart cam formations (34, 35) and an intermediate circular cylindrical portion located between the cam formations (34,35), wherein the first and second cam formations (34,35) are rotatably journalled in a first and second seating aperture (37, 38), respectively, in the housing on opposite sides of the drawbar, whereas the intermediate circular cylindrical portion is extended through the drawbar aperture, wherein each of the cam formations (34,35) comprises a first cam surface (34', 35'), each having the same cam pitch per angular measure and being operable to urge the drawbar rearward to a locked position, in which it firmly locks the tool holder shank to the clamping device, as well as a second cam surface (34", 35"), each having the same cam pitch per angular measure and being operable to positively displace the drawbar forward to an unlocked position in which the tool holder shank is releasable from the clamping device, wherein the drawbar is insertable into the bore through the forwardly facing surface, and wherein the second cam formation has a smaller cross sectional dimension than the first cam formation, such that the second cam formation is insertable through the first seating aperture and the drawbar aperture during mounting of the drawbar into the clamping device. a housing having a forwardly facing surface and a bore intersecting the forwardly facing surface and extending rearwardly therefrom for receiving the tool holder shank; a drawbar being mounted reciprocally movable inside the bore and which in a forward end comprises engagement means which is adapted to go into engagement with an engagement formation inside the 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 first and second spaced apart cam formations (34, 35) and an intermediate circular cylindrical portion located between the cam formations (34,35), wherein the first and second cam formations (34,35) are rotatably journalled in a first and second seating aperture (37, 38), respectively, in the housing on opposite sides of the drawbar, whereas the intermediate circular cylindrical portion is extended through the drawbar aperture, wherein each of the cam formations (34,35) comprises a first cam surface (34', 35'), each having the same cam pitch per angular measure and being operable to urge the drawbar rearward to a locked position, in which it firmly locks the tool holder shank to the clamping device, as well as a second cam surface (34", 35"), each having the same cam pitch per angular measure and being operable to positively displace the drawbar forward to an unlocked position in which the tool holder shank is releasable from the clamping device, wherein the drawbar is insertable into the bore through the forwardly facing surface, and wherein the second cam formation has a smaller cross sectional dimension than the first cam formation, such that the second cam formation is insertable through the first seating aperture and the drawbar aperture during mounting of the drawbar into the clamping device.