FOUNDING; FOUNDRY 



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acts directly upon the sand without the intervention of any pattern or mould. In any 

 large foundry there is an enormous accumulation of costly wheel-patterns, taking up 

 a great deal of space, and these can now be dispensed with by substituting the wheel 

 moulding-machine. Railway chairs are moulded in a machine ; and ploughshares, 

 which although only weighing a few pounds each, are sold at the low rate of 81. a ton, 

 are moulded in a machine. 



Plate Casting. Under the next class of improvements the introduction of plate- 

 casting has been the most fruitful of good results. 



One great source of expense and trouble in a foundry is the injury done to patterns 

 and to their impressions in the sand by the necessity, under the ordinary system of 

 moulding, of striking the pattern, or pushing it first in one direction and then in 

 another in order to loosen it. Now, the object of the machinist is to construct all 

 his spindles, bearings, bolts, and wheels, of specified sizes, and then to cast the framing 

 of his machine so accurately that the working parts may fit into the frame without 

 any manual labour. In order to effect this, every projection and every aperture in 

 the casting must be at an exact distance, and this can only be attained by employing 

 such a system as that of plate-casting, where the pattern is attached firmly to a plate, 

 and it is impossible for the moulder to distort or injure the impression. Plate-casting 

 has been long known, but was practically confined for many years to the production 

 of small articles, such as cast nails and rivets. 



In a plate-mould for rivet-casting, the shafts of the rivets are attached to one side of 

 the plate, which is f -in. thick, and planed on both sides. The heads of the rivets are 

 on the opposite side of the plate. The guides on the upper and lower flask admit 



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A, sand. 



B B, flask. R R, rivet pattern. 



P, plate. 



tho plate to fit between them, and when the plate is withdrawn the upper and 

 lower flasks close perfectly, and are in all respects like ordinary moulders' flasks. 

 The principle of moulding is very simple, and can be performed without skilled 

 labour ten times as fast as ordinary moulding, and with far greater accuracy. 

 The plate is inserted between the upper and lower flasks, and sand is filled in; 

 the plate is then withdrawn by simply lifting it ; the guides prevent any shaking 

 in this operation ; when the flasks are closed, the impression of the head of each 

 rivet is exactly perpendicular to its shaft. The first expense of patterns and 

 plates of this description is large, but the accuracy and rapidity of the process of 

 moulding is so advantageous as to cause us to look to the applications of plate-castings 

 becoming very extensive, since the requirements of the machine-maker demand every 

 year better castings at lower prices. 



When both sides of a pattern are symmetrical one-half only need be attached to 

 the smooth plate, the other face of the plate being left blank. An impression of the 

 pattern must be taken off both in the upper and lower flask, and when these are united 

 the result will be the same as if both sides of the plate had been moulded from. For 

 unsymmetrical patterns both sides of the plate must be employed. The system of 

 using plates with apertures in them, through which patterns could be pushed and 

 withdrawn by means of a lever, was first employed in casting brass nails. A modifi- 

 cation of this system has been extensively employed at Woolwich for moulding shot 

 and shells, in the following manner: 



SMI Casting. A circular aperture is made in a horizontal planed plate of iron, 

 two inches thick. Through this a sphere of iron, of the same diameter as the aper- 

 ture, is pushed until exactly a hemisphere appears above the plate. The lower flask 

 is put on to the plate, and sand filled in ; the lever being relieved, the sphere falls by 

 Its own weight; the lower flask is removed, and the upper flasjc put on the plate ; the 



