20 rotates on the ring 19 and drives it as a result so that the rpm of the ring 19 increases slowly and steadily in case of a start up spindle speed which lies below the operational speed of the spindle 13 provision can be made that after a predetermined time the drive of the spindle by the driving arrangement 24 be concluded by removing it and turning off the motor so that then the tangential belt 23 will again bring the spindle 13 from its intermediate rpm very quickly up to the operational rpm also in many cases the motor 32 can be advantageously controlled in such a way that it increases the spindle rpm slowly up to the operational rpm in the case where the operator controls the motor 32 advantageously a manually operable operating button for controlling the rpm can be disposed on the driving arrangement 24 whereby the operator can visually control the motor 32 in a suitable manner on the basis of his experience whenever the motor 32 has only a single rpm operating then this can be made effectively in such a way that the driving arrangement 24 drives the spindle 13 say at half its operating speed in that case the restart takes place in such a way that after release of the spindle brake 21 the motor 32 quickly raises the spindle 13 to the intermediate rpm determined by it and then drives the spindle for a sufficiently long time at this intermediate rpm which is made in such a.