Abstract: A high pressure apparatus for the manufacture of diamonds includes a pressure chamber formed of holes in annular, disc-like members arranged one after the other and a pair of opposed pressure-exerting members movable into the chamber formed by the holes with compressible gaskets arranged between adjacent disc-like members. The pressure exerting members are frusto-conical and the ends of the holes adjacent these members are similarly shaped.

Abstract: In the hydrostatic extrusion of tubes in a press which has a pressure chamber containing a high pressure cylinder, a pressure generating portion insertable into the cylinder, a die arranged in the cylinder and a mandrel axially fixed in relation to the die and composed of a carrier portion and a tip, and in which the tip forms with the opening in the die a gap in which a tubular billet is shaped into a tube by hydrostatic extrusion, in connection with the insertion of the tubular billet, a seal is produced initially between the mandrel and the hole in the billet at a point between the front part of the mandrel carrier and the hollow wall of the billet. This may be done by producing a constriction of the front end of the hole in the billet before the mandrel is inserted therein or by upsetting the billet against the die.

Abstract: A grinding element having a grinding section comprising diamond particles individually embedded in a resin binding medium with improved performance characteristics is provided, along with a method of making same. The improved characteristics are obtained by utilizing a metal coating on the diamond particles in the grinding section, which metal coating has a thickness of between 0.5 and 25 microns, preferably 5 to 20 microns, to impart to the section superior grinding properties to those which can be obtained with a like section wherein the diamond particles are not so coated.