High pressure producing apparatus

An apparatus for producing high pressure comprising a multi-die system wherein each die is made up of two cooperating parts arranged along the longitudinal centerline thereof, one part being a working body with one end thereof adjoining a solid medium plastic under pressure adapted to enclose a test sample subjected to a pressure transmitted by the solid medium thereto upon the dies being driven towards each other, the other part being a base member with one end thereof facing a die driving means common to all the dies and with the other end thereof facing another end of the working body and spaced a certain distance therefrom, the space between said ends being filled with a solid medium plastic under pressure, the surfaces or faces of said last-mentioned ends having identical annular grooves, the axes thereof essentially coinciding with the longitudinal centerline of the die, the inner edges of said grooves defining central portions of the working body and the base member ends respectively, the grooves being at least partially filled with a solid medium plastic under pressure, characterized in that the working body (4) of each die (2) is made up of two parts in the direction essentially perpendicular to the longitudinal centerline (3) of the die (2), the parts being a central insert (21) and an encircling ring (22) both arranged coaxially and capable of relative displacement towards the test sample (7), whereas the surface area of the end (23) of the central insert (21) adjoining the end (11) of the working body (4) is provided with the groove (14) approximates to or less than the surface area of the central portion (18) of said end (11).