Provided herein is an apparatus for detecting vibrations in a machine tool having a rotor portion (2) which is provided with tool members (5) and defines an axis of rotation (2a), the apparatus comprising a sensor assembly (3) which is able to rotate together with the rotor portion (2) and is designed to issue signals correlated to the vibrations, and a supporting and amplification device (6) for supporting the sensor assembly (3) and for amplifying the vibrations, which is set between the sensor assembly (3) and the rotor portion (2) and has a rotational asymmetry about the axis of rotation (2a) for any angle smaller than a full circle.