effect of the application of these high pressures is to stretch the whole machine especially between the plates 14 and 16 which are subjected to the hydraulic pressure and the end plate 13 slides a corresponding small amount e g about 0 005 inch on the table top 10 the movement detector constituted by the lever is now adjusted until the switch is just positively operated by a movement of this extent it will be seen that detection by this means is extremely positive in that it is only effective if the required pressure is applied and then only if this pressure is applied via the closed dies since otherwise the body of the machine cannot stretch this may be contrasted with an arrangement for example in which the hydraulic pressure is measured the maximum pressure will be obtained and indicated even in cases where the dies may be jammed open although in this specific embodiment a mechanical movement detector has been described comprising a lever system providing amplification of the dimensional change of the machine frame other detectors can be employed such as optical or electrical devices used for measuring and indicating small mechanical displacements the pump is now moved longitudinally by operation of the adjusting nuts 46 until the pump nozzle 43 is pressed sufficiently firmly into the rear recess 42 in the die.