is mounted on a slide face 35 of the base body 5 to be shiftable in the x direction on its upper face 36 the head plate 34 has for each punch a respective supporting region 37 which lies in a common plane with the supporting face 30 of the socket 28 of the coupling elements 19 when the latter are in a position which defines the retracted position a of the punches the head plate 34 has for each punch an aperture 38 through which the respective coupling element 19 may pass and which adjoins the supporting region 37 on its side oriented towards the coupling element 19 the supporting region 37 changes into a lead in chamfer at the edge of the aperture 38 an enlargement bay 38 a is provided which is adapted to receive the shank portion 21 of the respective punch when the head plate 34 is shifted underneath the respective punch head 20 the bay 38 a faces the open end of the opening 31 of the coupling element 19 and is disposed essentially as a linear continuation thereof for receiving the punch heads 20 the head plate 34 is shiftable in the x direction and the length of the displacement path of the head plate 34 is so dimensioned that the punch heads 20 are transferred from the coupling elements 19 to the head plate 34 when the driving unit 12 together with the head plate 34 is shifted in the x direction for disconnecting the driving unit 12 from the punches the head plate 34 is preferably connected with an arresting device which allows a displacement thereof only together.