A machine tool (10) comprises a revolving spindle (11). A plurality of tool holders (14) each of which is provided with a taper (13) and can be transferred by means of a gripper arm (20) from a magazine position remote from the spindle (11) and mounted by their tapers (13), one by one, in the spindle (11) in a machining position, while the other tool holders (14) remain in the magazine position. In order to avoid that metal chips may get into contact with and stick to the tapers (13) of the tool holders (14) while the latter are in the magazine position the tool holders (14) are accommodated in a cavity (40) providing a closed cover at least for the tapers (13).
