Abstract: In the radially adjustable tool head there is provided a radially adjustable slide serving to accommodate a cutting tool. The slide is arranged to slide on a spindle insert at guiding members containing guiding or guide surfaces which slide in pairs upon each other. To positively retain the slide on the spindle insert springs are arranged in such a manner and with a pre-bias such that the guiding surfaces are pressed against each other. Also, structure is provided to interrupt, when desired, the transmission of the pre-bias to the guiding surfaces.

Abstract: The pretensioning element serves to elevationally position or pretension or bias a circulation track bearing member. In order to reduce the requirements imposed upon the support and mounting surfaces during manufacture, with regard to alterations in parallelism during pretension adjustment and during load changes, that is in the range of elastic deformation, there is provided a housing which comprises at least one guide track. Two wedge members are displaceably guided in the guide track by means of tightening screws or bolts. The wedge members contain first wedge surfaces. A support plate is provided and comprises two second wedge surfaces which cooperate with the first wedge surfaces of the wedge members.