An apparatus is provided for compensating for such deformations as occur in operation in first and second clamping surfaces intended for a tool in a press. The clamping surfaces are reciprocally moveable towards and away from one another in order to move a first and second part of the tool towards and away from one another, and the first and second tool parts have a first and second abutment surface for abutment against the first and second clamping surfaces and the deformations cause uneven pressure in at least one contact region between the tool and the clamping surfaces. According to the present invention, there is disposed, in at least one contact region between a clamping surface and an abutment surface, a power unit which, on activation, is operative to press, away from the clamping surface located in the contact region at least a part of the abutment surface of the tool located there.