Adjustable torque screwdriver with thread colour marking - has colour liq. control unit with pump thruster and associated piston

A screwdriver has a defined adjustable torque. It has a face tooth coupling, the first part of which is connected to the screwing tool, and the other part, when the torque is reached, executes an axial movement relative to the first part. This second part transmits a control movement to a component which causes coloured fluid to be fed out from a supply source in the screwdriver and make a marking on the screw threads. There is a colour channel passing through the screwdriver, and in it is a valve preventing flow-back of the coloured fluid. The colour control unit has a pump thruster (6) with an associated piston (14). Between the piston (14) and pump thruster (6) is a defined dead intermediary space (15).