These are used in the production of various kinds of hollow ware, such as vases, lamp bodies, match safes, etc. The metal may be Britannia ware, silver, or soft brass. The die is generally a casting of soft close-grained iron. It is made in several parts, as it is necessary to open it in order to get the piece out.
Fig. 383 shows a die of this description. The plunger works down through the knurled sleeve, thus causing the confined fluid, with which the piece has been filled, to force the metal out into the impressions in the mold.
Fig. 383. Fluid Die Showing Plunger and Mold.
It is the custom in some factories to use soft rubber in place of the water or other fluid, the plunger pressing on it and thus swelling the metal out into the die. It is claimed that in producing clear-cut outlines and full, sharp corners, the rubber works better than a fluid.