upper and lower abutment faces 21 and 22 respectively the piston face 20 and the cylinder face 21 limit the displacement chamber 19 of the control cylinder 17 this chamber is connected to an air container 25 which is supplied from a compressed air source 39 via a filter 28 regulating valve 27 and lubricator 26 when the piston 18 is in contact with the lower cylinder face 22 the stop 23a associated with the piston rod 23 actuates the switch 24 a control pin 31 is mounted adjacent to the matrix 8 on the movable pressing table 9 as shown the opposite end of the movable table 9 is arranged to have a chamfered portion 34 that functions as a camming means thus on upward movement of the table 9 the camming means 34 can operate the switch 33 if desirable the device operates in the following manner at the beginning of the stamping process the chamber 19 of the control cylinder 17 is acted on by compressed air via the line 35 the pressure of this compressed air is greater than the pressure in the lines 16 and 15 which is required to raise the main piston 37 and the pressing table 9 as a result the pressure fluid supplied via the line 36.