Abstract: An apparatus is proposed for connection of workpieces using the friction stir welding method, with a shaft (33, 33?) which can be driven such that it rotates and at whose end remote from the drive end of the shaft a pin-like projection (8) is arranged, at whose end a first stop, which is formed by a first shoulder (6), is arranged, with the first shoulder having a diameter which is larger than the diameter of the pin-like projection (8), and with a second stop (7, 7?), which is formed from a second shoulder and is arranged such that the workpieces (19) to be connected can be enclosed between the stops (6, 7, 7?), in that at least one of the stops can be moved translationally in order to enclose the workpieces (19) with a predetermined force in the direction of the other stop.