An adapter or coupling is joined up with a flexible pipe made up of three pipes nested in each other whose end furthest from the coupling is joined up with an air-powered grinding tool or machine for clearing dust therefrom by aspiration. Furthermore the grinder is joined up by way of the three-part pipe and the coupling with pipes for supplying pressurized air to it and for carrying away such air after undergoing expansion in the motor of the grinder. The coupling has at one end or side three connection units for joining it up with the three-part pipe and two side unions for the supply of pressurized air and for carrying away such air after expansion. The opposite side of the coupling has further unions for joining it up with a flexible aspiration pipe.
