Stamping Metals
Many kinds of metal-work formerly bent into shape by the hammer and punch are now struck into shape by means of a pair of dies--one relief, the other intaglio,--between which the metal is pressed. Articles of considerable size are now made in hydraulic presses by means of a number of graduated dies, each pair coming gradually nearer the desired shape, but none of them making an impression deep enough to strain the metal. Stamp-mill is used chiefly for crushing or bruising ores, and consists of several vertical shafts which are made to descend with force by either water or steam power. See ORES.
Stands for Moulds are contrivances for blocking parts of moulds above the floor. Too often these are simply a makeshift. An excellent stand is readily made by moulding an open-sand ring about 18 to 24 inches diameter, in which are cast three or more vertical rods with their top ends leaning inwards, so that when the ring has been cast the whole may be reversed, and the loose ends cast into another open-sand mould about 6 or 8 inches diameter and of sufficient depth to bind all the rods firmly together. There is hardly any limit to the usefulness of these stands, as they may be made to any height convenient at a slight expense.
Starch is found in the grains, seeds, roots, pitch, and bark of plants. It is a snow-white, glistening powder when pure; its round or oval grains varying in size from 1/100 to 1/4000 of an inch in diameter. The granules of potato are larger than those of rice or wheat. Starch is insoluble in cold water, alcohol, or ether, but swells up and is converted into a paste in water containing 2 per cent of alkali. If heated in water to 140 deg.; the grains swell and burst, producing gelatinous starch, or amadin. Starch from grain is prepared by mixing the meal with water to a paste and washing the mass upon a sieve; a white insoluble substance called gluten is then left. This gluten in wheat-flour is extremely tenacious and elastic, and this is why free sands are made adhesive and strong by its use. See FLOUR; GLUTEN.