Bore clamp for clamping a workpiece comprising a workpiece bore located in the workpiece, with a) a clamping bush for engaging in the workpiece bore, the clamping bush being radially expandable, preferably with several separate clamping segments which are arranged distributed over the circumference of the clamping bush, b) a clamping bolt which extends coaxially through the clamping bush and is axially displaceable in a clamping direction between a clamping position and an unclamping position, b1) where the clamping bolt radially expands the clamping bush in the clamping position in order to clamp the clamping bush in the workpiece bore, b2) whereas the clamping bolt does not radially expand the clamping bush in the unclamping position so that the clamping bush can be inserted into the workpiece bore or pulled out of the workpiece bore, c) a clamping bolt drive (5, 6, 10-13) for axial displacement of the clamping bolt in the clamping direction into the clamping position, and d) a pneumatic position sensing for pneumatic detection of the clamping position and the unclamping position, characterized in e) that the clamping bolt drive (5, 6, 10-13) comprises the following: e1) a piston laterally displaceable with respect to the clamping direction, and e2) a wedge gear (10, 13) with wedge faces (10, 13) sliding on one another for converting the lateral movement of the piston into a corresponding axial movement of the clamping bolt in the clamping direction, and f) that the pneumatic position sensing comprises the following: f1) the tension bolt, f2) the cylinder in which the tension bolt is displaceable along the clamping direction, f3) a first compressed air line which opens into the cylinder substantially axially at a first opening from the workpiece side, • wherein the first opening of the first compressed air line is closed by the tension bolt in the unclamping position, in particular by means of a sealing element in the tension bolt, • whereas the first opening of the first compressed air line is released by the tension bolt in the clamping position. a) a clamping bush for engaging in the workpiece bore, the clamping bush being radially expandable, preferably with several separate clamping segments which are arranged distributed over the circumference of the clamping bush, b) a clamping bolt which extends coaxially through the clamping bush and is axially displaceable in a clamping direction between a clamping position and an unclamping position, b1) where the clamping bolt radially expands the clamping bush in the clamping position in order to clamp the clamping bush in the workpiece bore, b2) whereas the clamping bolt does not radially expand the clamping bush in the unclamping position so that the clamping bush can be inserted into the workpiece bore or pulled out of the workpiece bore, b1) where the clamping bolt radially expands the clamping bush in the clamping position in order to clamp the clamping bush in the workpiece bore, b2) whereas the clamping bolt does not radially expand the clamping bush in the unclamping position so that the clamping bush can be inserted into the workpiece bore or pulled out of the workpiece bore, c) a clamping bolt drive (5, 6, 10-13) for axial displacement of the clamping bolt in the clamping direction into the clamping position, and d) a pneumatic position sensing for pneumatic detection of the clamping position and the unclamping position, characterized in e) that the clamping bolt drive (5, 6, 10-13) comprises the following: e1) a piston laterally displaceable with respect to the clamping direction, and e2) a wedge gear (10, 13) with wedge faces (10, 13) sliding on one another for converting the lateral movement of the piston into a corresponding axial movement of the clamping bolt in the clamping direction, and e1) a piston laterally displaceable with respect to the clamping direction, and e2) a wedge gear (10, 13) with wedge faces (10, 13) sliding on one another for converting the lateral movement of the piston into a corresponding axial movement of the clamping bolt in the clamping direction, and f) that the pneumatic position sensing comprises the following: f1) the tension bolt, f2) the cylinder in which the tension bolt is displaceable along the clamping direction, f3) a first compressed air line which opens into the cylinder substantially axially at a first opening from the workpiece side, • wherein the first opening of the first compressed air line is closed by the tension bolt in the unclamping position, in particular by means of a sealing element in the tension bolt, • whereas the first opening of the first compressed air line is released by the tension bolt in the clamping position. f1) the tension bolt, f2) the cylinder in which the tension bolt is displaceable along the clamping direction, f3) a first compressed air line which opens into the cylinder substantially axially at a first opening from the workpiece side, • wherein the first opening of the first compressed air line is closed by the tension bolt in the unclamping position, in particular by means of a sealing element in the tension bolt, • whereas the first opening of the first compressed air line is released by the tension bolt in the clamping position. • wherein the first opening of the first compressed air line is closed by the tension bolt in the unclamping position, in particular by means of a sealing element in the tension bolt, • whereas the first opening of the first compressed air line is released by the tension bolt in the clamping position.