Device for holding an ancillary device at right angles to an imaginary axis of rotation

A device for holding an ancillary device at right angles to an imaginary axis of rotation, more particularly a tool holder for face milling a brake disc present on a vehicle, the device comprising:

• a coupling section which can be connected to a shaft or hub rotating around the axis of rotation, as well as a support for supporting the ancillary device, and means for holding the ancillary device at right angles to the axis of rotation, which holding means comprise a hinge construction according to the spherical hinge principle which comprises two parts, a first part of which having a sphere function and the second part of which having a scale function, one of the parts being connected to the coupling section and the other part being connected to the support, the device further including adjusting means for adjusting the support at right angles to the axis of rotation, which adjusting means during the rotating of the coupling section can tilt the support in a time-continuous manner around two tilting axes which are arranged at an angle to each other through a centre of an imaginary sphere through the contact faces of the first and second parts, and the adjusting means comprising operating means which are substantially stationary relative to the firm object, and comprising turning means for turning the support relative to the coupling section around an imaginary rotary shaft at right angles to the imaginary axis of rotation, the turning means resting against the support and the coupling section, characterised in that the device further includes a protractor which is attached to the support and produces a signal that is indicative of the orientation of the support relative to an imaginary horizontal face.