The present invention relates to a manually operated machine-tool, fitted with a disc-shaped tool (18) and a housing (10) for accomodating a work spindle (13), the free end of which (131) bears the tool (18) between a clamping ring (19) and a securing nut (20), both featuring together a securing device (17). The machine is also fitted with a locking device (25) to prevent the spindle (13) from rotating. The locking device has a crown, mounted on the clamping piece, with a least one notch (28), as well as a hand lever (29) provided with a latch tooth (32) to engage the notch (28). For a safer change of tool on the machine, the SDS-click clamping ring (19), as modified according to the standard EP 0 424 388, is captive, torsion-proof and can be fixed to the drive spindle (13) by putting a hexagon socket on an external hexagonal socket head screw, superficially locked in the direction of rotation of the work spindle (13) up to a certain number of rotations by the work spindle (13), and, starting from a given number of rotations, actuated through gearing by means of a spindle-locking device (25) and put in a release position.