Apparatus and method of forming countersinks and/or mouse holes in a stamped high strength aluminium sheet

Method of forming countersinks and/or mouse holes comprising the steps of obtaining by stamping a sheet of a first high strength aluminium alloy in a T4 tempering state, the sheet comprising at least a through hole or a notch, inserting a copper refrigerated tool through the hole or notch such that the tool protrudes at least from one surface of the sheet and fits snugly in the through hole or notch, depositing by a DED process a portion of a second high strength aluminium onto the sheet around the through hole and/or notch to form a countersink and/or a mouse hole. The method comprises refrigerating the tool to maintain the maximum instantaneous surface temperature of the tool below 300°C and cool down the temperature of the tool to below 100°C in less than 2 seconds when the weld portion of the second alloy starts solidifying.