A device for solid state joining of light metals like aluminum is described. The device utilizes the principle of continuous extrusion to add a string of filler metal into a groove separating the components to be joined, and shear deformation for surface oxide removal in the groove. The device comprises a rotating drive spindle (13) terminated in a drive spindle head (14). A groove with the shape of a circular arc constituting an extrusion chamber (16) is machined in the outer surface (15) of the drive spindle head (14), the extrusion chamber (16) being limited radially outwards by a stationary annular metal shoe (17) surrounding the drive spindle head (14), the extrusion chamber (16) being terminated by an integrated (fixed) or replaceable abutment member (18) for diverting aluminum from its circular movement in the extrusion chamber (16) through a die orifice (19).
